Author Topic: UT61E Auto Power Off Modification  (Read 36070 times)

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Offline DeanA

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UT61E Auto Power Off Modification
« on: July 16, 2012, 12:09:55 pm »
I have come up with a relatively simple modification to the UT61E which enables the auto power off. Another small modification to the RS232 interface board automagically disables the auto power off when connected to the P.C.

When the RS232 data out function is enabled on the ES515922 by connecting the RS232 pin (pin 111) to V- the auto power off function is disabled. On the UT61E the RS232 output is permanently enabled with a PCB connection from pin111 to V-.
Fortunately the UT61E optical isolation port for the PC interface has a clear window for 2, 3mm LEDs and only the transmit LED is fitted. I added an 3mm NPN IR phototransistor to the spare optical port with the collector connected to the RS232 enable pin (pin 111) and emitter connected to V-.

The RS232 interface board also has a spare window position for a TX LED from the PC. The interface PCB even has a position for the 3mm TX LED connected between V+ and TXD from the PC which is not fitted. I fitted a 3mm IR LED and a 10K current limiting resistor to the interface board. The TXD line from the PC idles low so the IR LED is permanently on when connected to the PC.

So now, when the interface board is slid into the optical port of the UT61E the IR photo transistor added to the UT61E turns on and connects the RS232 enable pin to V-. This enables the RS232 output and disables the auto power off mode of the meter. The PC icon in the bottom left hand corner should turn on when the RS232 optical port is connected to the UT61E with the interface software connected.
The UT61E interface software should be running for everything to work because the RS232 handshaking lines must be in the correct state to power up the RS232 interface board.

More details can be viewed here www.designelectronics.com.au/DesignElectronics_UT61E-APO.htm.

Regards,
Dean


Offline ModemHead

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Re: UT61E Auto Power Off Modification
« Reply #1 on: September 18, 2012, 01:52:05 pm »
Thanks much for posting this information.  Using it I was able to easily modify my UT61E to regain it's APO functionality.

I didn't have a 3mm IR LED, so I used a clear red high-efficiency LED in the RS232 interface module. I used a junkbox photo-transistor in the meter, affixed to the circuit board with some plastic-repair putty.  This keeps from having fiddly little wires connecting the two halves of the case.  It all works nicely.  Data output is enabled immediately when the software turns on the RS-232 handshake lines.

The LCD even has an APO icon, which is now on, and the data-output icon is off. I notice that the APO icon goes off if you hold the yellow button down when turning on the meter.
 

Offline T4P

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Re: UT61E Auto Power Off Modification
« Reply #2 on: September 18, 2012, 03:34:13 pm »
Did you guys use a dremel and attack the interface module or what?  :P
 

Offline ModemHead

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Re: UT61E Auto Power Off Modification
« Reply #3 on: September 18, 2012, 04:53:08 pm »
Did you guys use a dremel and attack the interface module or what?  :P
I scored the seam around the module by repeatedly dragging a hobby (X-acto) knife backwards across all four sides.  When the scores were deep enough, the module came apart easily with just a little persuasion from a spudger. Not a job for the impatient, but not really difficult, either.

Despite being careful, during my handling of the module I managed to damage one of the SMD transistors, and had to replace it.  So I would recommend a soft touch, which might rule out power tools.

A little dab of CA gel on each corner put it back together.
 

Offline T4P

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Re: UT61E Auto Power Off Modification
« Reply #4 on: September 18, 2012, 06:55:10 pm »
Did you guys use a dremel and attack the interface module or what?  :P
I scored the seam around the module by repeatedly dragging a hobby (X-acto) knife backwards across all four sides.  When the scores were deep enough, the module came apart easily with just a little persuasion from a spudger. Not a job for the impatient, but not really difficult, either.

Despite being careful, during my handling of the module I managed to damage one of the SMD transistors, and had to replace it.  So I would recommend a soft touch, which might rule out power tools.

A little dab of CA gel on each corner put it back together.
Xacto knife wasn't working for me so i took out my cordless drill and my small saw bit, worked well and nothing broke. Just sawed a side and used a flat screwdriver to nudge it out ... Everything's intact
 

Online Monkeh

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Re: UT61E Auto Power Off Modification
« Reply #5 on: September 18, 2012, 08:07:54 pm »
I just slid a small (but not flimsy) knife blade in at a corner, glue broke easily.
 

Offline Amarbir[Lynx-India]

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Re: UT61E Auto Power Off Modification
« Reply #6 on: September 18, 2012, 08:19:04 pm »
Dean ,
 Very Very interesting .If i can ever lay my hands on the same i will definately try this out .On the other hand 30 minutes shutdown would kill the battery soon 15 minutes auto power off is more then enough i think imho  .
Regards

Amarbir Singh Dhillon [ Lynx-India ] , Chandigarh [ India ] - > www.lynxdealerstore.com , www.lynx-india.com
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Offline T4P

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Re: UT61E Auto Power Off Modification
« Reply #7 on: September 19, 2012, 06:03:32 am »
Huh? In sleep the chip draws next to nothing? (2.5uA-5uA)
And in operation without RS232 on would be more like measured in uA instead of mA
I already posted my findings on the UT61E thread and that's the fact. RS232 is always on without the mod and chews power
 

Offline torr032

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Re: UT61E Auto Power Off Modification
« Reply #8 on: October 07, 2012, 08:33:23 pm »
Is there perhaps a way to modify hold button for example and to force it in the standby mode?
 I don't find it's pretty convenient to turn knob all the way from one side to another, one single on/off button is more useful.
 

Offline DeanA

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Re: UT61E Auto Power Off Modification
« Reply #9 on: October 09, 2012, 07:15:20 am »

I didn't have a 3mm IR LED, so I used a clear red high-efficiency LED in the RS232 interface module. I used a junkbox photo-transistor in the meter, affixed to the circuit board with some plastic-repair putty.  This keeps from having fiddly little wires connecting the two halves of the case.  It all works nicely.  Data output is enabled immediately when the software turns on the RS-232 handshake lines.

You did a nice neat job of the meter modification, good idea keeping the photo transistor on the PCB too.

Regards,
Dean.

Offline onlooker

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Re: UT61E Auto Power Off Modification
« Reply #10 on: October 20, 2012, 01:20:16 am »
This is what I did to my new UT61E.  I think it is a simple and good DIY to share. What it does, in addition to the usual APO DIY, is to provide manual power on/off controls at any ON positions of the rotary switch without turning the switch (as other had already asked).

----The operations:

1). When the meter is on, pressing "hold" for 3 seconds to turn the meter off.

2). When the meter is off, pressing "range" to turn it on.

3). The normal "hold" and "range" functions are retained.

4). The APO DIY worked better (smaller off current).

5). Switching the rotary from "OFF" to "V" no longer turn on the meter. I do not feel the need to to retain this function, but if desired probably adding a cap somewhere should have it work again.

----The performance:

1). The off current is about 0.01uA.

In fact, the usual APO DIY by itself has severe problems in that the power off current is about 170uA (my test). For a 200mAh battery, this translates to about 1.5 month power retaining time without using the meter. To give an idea about how small 0.01uA is, it could be mentioned that the leak current of a Li battery with 10 years of shelf life is around 1uA.

2). The burden voltage is about 0.2mV.

3). This power on/off ctrl worked properly even when the battery is < 3V (did not test the meter accuracy at this voltage).

----The making:

Except for the Si4562, all other parts are taken from junk PCBs I had (a few).  That is why you see SMDs of different sizes. I bought Si4562 on ebay for about $0.35 each, but I had to buy 10 for this price. I also made a few goofs: cut a wrong trace on the meter PCB; broke a leg of the IC; a few wiring changes after soldered it to the meter and along the way burnt a corner of the res array.

Altogether, 2 traces on the meter PCB needs to be cut: the VB+ trace and the "range" button trace. The board needs only to be about 4x5 pads in size.

If you want to try this, make sure D1 has enough forward voltage drop or simply place 2 diodes or a zenor instead.

On a related note, for the APO-data link part of the DIY, the pull up resistor is not really needed. According to the datasheet, the RS232 pin was internally pulled up with a short current about 10uA. One can regard this as a resistor of a few hundred k connected to the positive voltage (~3V) rail. I used the photoresistor+red LED approach without the extra resistor.


« Last Edit: October 20, 2012, 02:01:37 pm by onlooker »
 

Offline onlooker

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Re: UT61E Auto Power Off Modification
« Reply #11 on: November 21, 2012, 02:38:34 am »
This is the version 2 of the auto/manual power switch schematic.  The motivation was simple: After watching Martin Lorton's video, I realized that there was a hidden function when holding down the "hold" button for a few seconds and, hence, I wanted to remove the use of the "hold" button. Along the way I also changed the schematic.

With the new schematic, manual power on/off was done with the same button. My preferred choice was the yellow VAHz button. The key points in my last email remained true.

I wanted to come up with a schematic that does not need to cut the button trace. But, with the parts I have and a limited time to experiment, it either has too large a power-off current (a few uA) or can't be switched reliably. On the other hand, at least, the new schematic does work.
 
 
 

Offline dr_p

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Re: UT61E Auto Power Off Modification
« Reply #12 on: April 20, 2013, 09:21:42 pm »
Just received my UT61E from Franky the other day. I decided I don't need a backlight on every meter, so I'll just do the "Auto power off" hack.


I did everything you guys did, but I used a photoresistor instead of a phototransistor. This I think is critical to what follows. Upon reassembly, the meter kinda froze when the optical port was exposed to light. All digits are off, but it keeps going through the functions.


I did some measurements and I think I found a big problem in your connections: the VB- you considered to be the positive pin of C33, but that is +6V. The chip is powered by 3V, and that is the voltage on the positive terminal of C31. So I reconnected everything and it works like a charm. I think your design pulled pin 111 lower than VB-, but some of the difference (0.7V) fell on the phototransistor, so it kinda worked.


What do you guys think?


[photo removed]

edit: I just noted Satan's quartz crystal :) )
« Last Edit: April 20, 2013, 10:34:40 pm by dr_p »
 

Online Monkeh

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Re: UT61E Auto Power Off Modification
« Reply #13 on: April 20, 2013, 09:57:33 pm »
You need to check the schematic. Negative side of C31 is V-, positive side of C33 is V+. Between them is GND.
 

Offline dr_p

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Re: UT61E Auto Power Off Modification
« Reply #14 on: April 20, 2013, 10:43:22 pm »
Yes, you are right about the capacitors. I removed the previous photo, since the captions were wrong.


But still, datasheet says pin 111 should be pulled to V- to enable serial comm, but doesn't say it has to be pulled to V+ to be idle.


Since the datasheet says "the HIGH an LOW voltage levels correspond to DGND an V- respectively" (Serial data output, p.21), maybe an inactive pin 111 is tied to DGND, so to the positive of C31.
« Last Edit: April 20, 2013, 10:45:30 pm by dr_p »
 

Online Monkeh

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Re: UT61E Auto Power Off Modification
« Reply #15 on: April 20, 2013, 10:51:39 pm »
You may be right, however, I haven't had any issues with mine.
 

Offline dr_p

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Re: UT61E Auto Power Off Modification
« Reply #16 on: April 20, 2013, 11:28:16 pm »
so here's the way it worked for me:


 

Offline rolandpenplotter

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Re: UT61E Auto Power Off Modification
« Reply #17 on: January 18, 2014, 10:14:05 pm »
Hello :)

I've just taken my UT61E apart in order to perform this mod, but I need some clarification which is not provided:

Where the track emerges out from the IC on pin 111, there is a via immediately where the track emerges from the IC; do I cut the trace *BEFORE* the via, or after the via, halfway across the loop to V- ?

If someone could make this crystal clear, I'd appreciate it :)

Thanks a lot folks :)


PS: There's a MUCH easier way to achieve the functionality provided by this mod:

1/ Put a magnet inside the RS232 head

2/ Glue a normally open (N/O) reed switch inside the meter, exactly in the area where the magnet will be when you connect the lead to the meter's recess, cut the track as per this guide, and connect the ends of the reed switch to the pins "111" and the "V-" pin, the trace between which, you have just cut.


;)
« Last Edit: January 18, 2014, 10:22:27 pm by rolandpenplotter »
 

Offline DeanA

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Re: UT61E Auto Power Off Modification
« Reply #18 on: January 19, 2014, 01:28:23 am »
Hi,
You need to cut the track before the via so that pin 111 only goes to your switch (whatever you are using, phototransistor, LDR or reed switch).
Regards,
Dean

Offline rolandpenplotter

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Re: UT61E Auto Power Off Modification
« Reply #19 on: January 19, 2014, 01:33:26 am »
Hi,
You need to cut the track before the via so that pin 111 only goes to your switch (whatever you are using, phototransistor, LDR or reed switch).
Regards,
Dean

Thanks Dean, you're a star mate :)
 

Offline rolandpenplotter

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Re: UT61E Auto Power Off Modification
« Reply #20 on: January 19, 2014, 08:08:00 pm »
I've just messed up my meter :'(

I was under the magnifier, preparing the tinning of the lead for the enamelled wire to pin 111, and a blob of solder wicked onto the pins... ARGH!

I tried and tried to suck off the solder, even using a solder sucking tool and by dropping a bigger blob of solder across the mess, and then sucking it off (this is all @ 350 degrees) and NOTHING works; a couple of the pads look a bit skewiff too, bummer!

To compound it, I have NO solder wick at all - I've never had it.

Anyone fancy a cheap, brand new UT61E for a minor repair? I'm just gonna buy a new one I think (well, how I feel right now I am):


 

Offline Legit-Design

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Re: UT61E Auto Power Off Modification
« Reply #21 on: January 19, 2014, 08:15:43 pm »
I've just messed up my meter :'(

I was under the magnifier, preparing the tinning of the lead for the enamelled wire to pin 111, and a blob of solder wicked onto the pins... ARGH!

I tried and tried to suck off the solder, even using a solder sucking tool and by dropping a bigger blob of solder across the mess, and then sucking it off (this is all @ 350 degrees) and NOTHING works; a couple of the pads look a bit skewiff too, bummer!

To compound it, I have NO solder wick at all - I've never had it.

Anyone fancy a cheap, brand new UT61E for a minor repair? I'm just gonna buy a new one I think (well, how I feel right now I am):

http://farm3.staticflickr.com/2824/12037402066_4d3678c352_b.jpg

Buy wick, buy flux -> profit!

Practice with some non critical/broken boards first. Practicing first is the best way to learn and succeed. Nothing is lost yet.
 

Online Monkeh

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Re: UT61E Auto Power Off Modification
« Reply #22 on: January 19, 2014, 08:20:37 pm »
 

Offline Legit-Design

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Re: UT61E Auto Power Off Modification
« Reply #23 on: January 19, 2014, 08:41:12 pm »
There is still pins left on the package and tracks on the pcb. Nothing that isn't too hard to fix. Just need to take a step back and make everything work properly, proper tools and all that. Good soldering iron with adjustable temperature, no more lifted pads. With proper technique and tools no force is required. Maybe start with EEVblog soldering tutorials. Get old computer motherboard or sound/display card and start soldering.
 

Offline rolandpenplotter

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Re: UT61E Auto Power Off Modification
« Reply #24 on: January 19, 2014, 09:34:38 pm »
There is still pins left on the package and tracks on the pcb. Nothing that isn't too hard to fix. Just need to take a step back and make everything work properly, proper tools and all that. Good soldering iron with adjustable temperature, no more lifted pads. With proper technique and tools no force is required. Maybe start with EEVblog soldering tutorials. Get old computer motherboard or sound/display card and start soldering.

Hello :)

I'm 38 and have been soldering since I was 5, on production lines and in TV repair (no, I wasn't working on a production line at 5 years old ^_^).

It's not my soldering that was the issue; I can solder in my sleep. I have a temp controlled anti-static iron - it was that I was rushing and not focusing on the task at hand, and I didn't have any wick or flux. Ah well, sold it now so it's now a non-issue, but thank you for replying.

Maybe I'll save up for a better UNI-T model with APO and backlight, like the UT71E :)
 

Offline Legit-Design

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Re: UT61E Auto Power Off Modification
« Reply #25 on: January 19, 2014, 11:14:14 pm »
Maybe I'll save up for a better UNI-T model with APO and backlight, like the UT71E :)

Beware, not all UNI-T meters are created equal (price-value).

I thought I would post my opinion of the UT61E now that I have one, especially in relation to the quality of the UT71E and compared to my other UNI-T meters and all my other experience with multimeters over the years. I have had mixed experiences with UNI-T. I now have four including the UT61E.

Now how would I compare it to the UT71E? Well in a nutshell, the UT71E at 3-4 times the price, is a heap of junk compared to the UT61E. Its input layout and protection is terrible. Mine came with accuracy of worse than 0.4% out of the box.
Bolded part.

When the price goes up there might be better options. Used Fluke will still work after decades of use and still worth money. Cheap meters lose their resale value faster.
 

Offline rolandpenplotter

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Re: UT61E Auto Power Off Modification
« Reply #26 on: January 19, 2014, 11:16:00 pm »
Maybe I'll save up for a better UNI-T model with APO and backlight, like the UT71E :)

Beware, not all UNI-T meters are created equal (price-value).

I thought I would post my opinion of the UT61E now that I have one, especially in relation to the quality of the UT71E and compared to my other UNI-T meters and all my other experience with multimeters over the years. I have had mixed experiences with UNI-T. I now have four including the UT61E.

Now how would I compare it to the UT71E? Well in a nutshell, the UT71E at 3-4 times the price, is a heap of junk compared to the UT61E. Its input layout and protection is terrible. Mine came with accuracy of worse than 0.4% out of the box.
Bolded part.

When the price goes up there might be better options. Used Fluke will still work after decades of use and still worth money. Cheap meters lose their resale value faster.

Thank you for that. However, that's just one person's opinion on it, but I do value it and will consider it IF I upgrade. :)
 

Offline Wytnucls

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Re: UT61E Auto Power Off Modification
« Reply #27 on: January 20, 2014, 05:19:00 am »
Perhaps Lightages has changed his mind since then.
The 71E model may not be what it's cracked up to be, but the 71D has been good for me over more than a year now. My 61E has cheaper components and drifts like crazy, making that last digit very unreliable.
If one can put up with its slow continuity test and flimsy input protection, I am convinced the 71D is one of the most cost effective meter for electronic bench work. AC+DC, 40,000 count, internal logging, hardly any drift and USB data connection are some of its most important features.
 

Offline torr032

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Re: UT61E Auto Power Off Modification
« Reply #28 on: February 18, 2014, 10:55:55 pm »
I have modded my 61E by cutting  pin111 to V- but it power off after 15 minutes of TURNING ON.

Is there a way to mod 61E to auto power off after some time of NON-USE ?
« Last Edit: February 18, 2014, 10:57:39 pm by torr032 »
 

Online Monkeh

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Re: UT61E Auto Power Off Modification
« Reply #29 on: February 19, 2014, 06:00:25 am »
I have modded my 61E by cutting  pin111 to V- but it power off after 15 minutes of TURNING ON.

Is there a way to mod 61E to auto power off after some time of NON-USE ?

It powers off 15 minutes after the last press of a button or change of mode. That's it.

Read the datasheet some time.
 

Offline grumpydoc

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Re: UT61E Auto Power Off Modification
« Reply #30 on: February 19, 2014, 08:55:52 am »
Quote
Is there a way to mod 61E to auto power off after some time of NON-USE
As above but how do you define "non-use" in a way that the meter could detect?

Other than mode switch changes, that is.
 

Offline G7PSK

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Re: UT61E Auto Power Off Modification
« Reply #31 on: February 19, 2014, 09:08:38 am »
I've just messed up my meter :'(

I was under the magnifier, preparing the tinning of the lead for the enamelled wire to pin 111, and a blob of solder wicked onto the pins... ARGH!

I tried and tried to suck off the solder, even using a solder sucking tool and by dropping a bigger blob of solder across the mess, and then sucking it off (this is all @ 350 degrees) and NOTHING works; a couple of the pads look a bit skewiff too, bummer!

To compound it, I have NO solder wick at all - I've never had it.

Anyone fancy a cheap, brand new UT61E for a minor repair? I'm just gonna buy a new one I think (well, how I feel right now I am):



If you need solder wick and don't have any to hand you can strip some multi strand wire and use that, works better if you have some flux but even then if don't have flux if you tin the very end enough flux creeps up the wire to enable that top work as solder wick.
 

Offline torr032

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Re: UT61E Auto Power Off Modification
« Reply #32 on: February 19, 2014, 09:48:48 pm »
Quote
Is there a way to mod 61E to auto power off after some time of NON-USE
As above but how do you define "non-use" in a way that the meter could detect?

Other than mode switch changes, that is.

its not very convenient when in the middle of the work meter starts beeping and then shut himself off. Even my cheap 9205 had auto power off that worked only after non-use.
 

Online Monkeh

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Re: UT61E Auto Power Off Modification
« Reply #33 on: February 19, 2014, 11:34:02 pm »
Quote
Is there a way to mod 61E to auto power off after some time of NON-USE
As above but how do you define "non-use" in a way that the meter could detect?

Other than mode switch changes, that is.

its not very convenient when in the middle of the work meter starts beeping and then shut himself off. Even my cheap 9205 had auto power off that worked only after non-use.

Please propose a reliable method to detect 'use' in all meter modes.
 

Offline dr_p

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Re: UT61E Auto Power Off Modification
« Reply #34 on: February 20, 2014, 07:32:15 am »
Please propose a reliable method to detect 'use' in all meter modes.

from the Amprobe AM-270 user manual:

Quote
Auto Power Off (APO)
The Auto Power Off (APO) mode turns the meter off automatically to extend battery life after approximately 17 minutes of no activities. Activities are specified as:
   1) Rotary switch or push button operations, and
   2) Significant measuring readings of above 10% of range or non-OL ohms readings.
 

Online Monkeh

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Re: UT61E Auto Power Off Modification
« Reply #35 on: February 20, 2014, 07:34:13 am »
Please propose a reliable method to detect 'use' in all meter modes.

from the Amprobe AM-270 user manual:

Quote
Auto Power Off (APO)
The Auto Power Off (APO) mode turns the meter off automatically to extend battery life after approximately 17 minutes of no activities. Activities are specified as:
   1) Rotary switch or push button operations, and
   2) Significant measuring readings of above 10% of range or non-OL ohms readings.

And how well will #2 work with an input impedance in the gigaohms in the mV range?
« Last Edit: February 20, 2014, 07:38:01 am by Monkeh »
 

Offline grumpydoc

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Re: UT61E Auto Power Off Modification
« Reply #36 on: February 20, 2014, 08:23:45 am »
Quote
Significant measuring readings of above 10% of range or non-OL ohms readings.
Splitting hairs, I know, but having readings above 10% of range does not reliably indicate use (eg left connected to a voltage source and forgotten about) nor do readings below 10% of range reliably indicate non-use (eg, monitoring the output of a bridge).

I agree it probably works well enough in practice.
 

Offline torr032

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Re: UT61E Auto Power Off Modification
« Reply #37 on: February 20, 2014, 11:52:39 pm »

Please propose a reliable method to detect 'use' in all meter modes.
[/quote]

I don't know really I never thought how it is  implemented in a multimeter. Even in cheap dt9205 auto power off worked fine for me.
 

Offline Steps

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Re: UT61E Auto Power Off Modification
« Reply #38 on: January 14, 2015, 12:37:46 pm »
Hello everybody!
I going to do power off mod and backlit mod (with permanent light, not original). And I want that light will be off after DMM going to sleep. Can I connect +V of the LEDs to the positive side of C33, like for the IR transistor?
And should I add driving the backlight leds with transistors like in UT60E schematic?
« Last Edit: January 15, 2015, 07:55:18 am by Steps »
Sergey
 

Offline DeanA

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Re: UT61E Auto Power Off Modification
« Reply #39 on: January 17, 2015, 07:37:23 am »
Hello everybody!
I going to do power off mod and backlit mod (with permanent light, not original). And I want that light will be off after DMM going to sleep. Can I connect +V of the LEDs to the positive side of C33, like for the IR transistor?
And should I add driving the backlight leds with transistors like in UT60E schematic?
Hi,
I don't think I would use positive side of C33 for the anode of the LED backlight.  According to ES51922 datasheet pin 1 and 2 (C33+) is the output of on-chip DC-DC converter and we don't know how much current that can supply.  I would probably use VC+ (C36+ 10uF) for the backlight anode. 
For switching the backlight on/off I think you have a couple of options.
1.  If you want the backlight on all the time except during sleep you could probably use pin 58 "SLEEP".  Datasheet says "asserts low in SLEEP mode" so you could probably connect to the base of a NPN transistor to this pin58 (with a base resistor) and use the collector to drive the cathode of the backlight (with dropping resistor).
2.  There is a backlight enable output on the ES1922, pin105 "BKOUT".  ES1922 datasheet says "this pin will change from -3V to +3V for 60sec once press BKLIT".  So then you need a switch (use hold switch?) on the "BKLIT" pin102 to pulse it low.  Looks like you can change the time from 60sec to 180sec using "BKSEL" pin113.  So you could connect the base of a NPN transistor to this pin105 and use the collector to drive the cathode of the backlight (with dropping resistor).

BTW, I was stupid enough to insert a 9V battery reverse polarity to my UT61E and left it on for a while without checking it.  It took out the tant C36 from reverse polarity and blew a hole in the regulator W1, 7201U30.  I replaced the 10uF Tant and the regulator with a MCP1703T (cause that's what I could get in the same package from element14).  All working again now so I'm glad it didn't take out the main controller IC.

Regards, Dean.
Disclaimer, I have not tried any backlight mods so can't say for sure if either of the above mods work.  I see there are other mods for UT61E backlight online, I haven't looked at them in detail so there could be better ideas there.

Offline Steps

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Re: UT61E Auto Power Off Modification
« Reply #40 on: January 19, 2015, 09:33:57 am »
Thank you Dean for the reply!
Very usefull information.  So I attached schema with NPN transistors (I took it from one of the UNI-T DMM's) Is it OK? What about value of the resistors? For me looks like to be ok.
And MJLORTON  http://mjlorton.com/forum/index.php?PHPSESSID=c9e3a97e51595b2fcfeae5b6f9a3f5b0&topic=284.msg2290#msg2290
did mod with LED connected directly to IC ES1922, but unfortunatly we do not have information regarding max current from pin105 "BKOUT".
Sergey
 

Offline DeanA

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Re: UT61E Auto Power Off Modification
« Reply #41 on: January 20, 2015, 10:28:10 am »
Thank you Dean for the reply!
Very usefull information.  So I attached schema with NPN transistors (I took it from one of the UNI-T DMM's) Is it OK? What about value of the resistors? For me looks like to be ok.
And MJLORTON  http://mjlorton.com/forum/index.php?PHPSESSID=c9e3a97e51595b2fcfeae5b6f9a3f5b0&topic=284.msg2290#msg2290
did mod with LED connected directly to IC ES1922, but unfortunatly we do not have information regarding max current from pin105 "BKOUT".

I don't know why they have used those 2 NPN transistors in that backlight switching circuit.  I think you should only need one NPN transistor from either pin58 "SLEEP" or pin105 "BKOUT" (depending on if you want the backlight on all the time or just the 60seconds from the BKOUT pin.  The resistor in series with the backlight will depend on the backlight you are using, how many series LEDs in the backlight? Then you probably want around 10mA through the backlight. So backlight series resistor = (9V - 3V X Number Of Series LEDs)/10mA.  For 1 LED backlight I would use around 600R, 2 LED Backlight 300R.  Go lower if you want the backlight brighter.  Base resistor can be 10K to 47K. 

Offline Steps

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Re: UT61E Auto Power Off Modification
« Reply #42 on: January 20, 2015, 11:05:00 am »
I am highly appreciate you, Dean, for your advices.

I don't know why they have used those 2 NPN transistors in that backlight switching circuit.
I guess for two levels of light.

I will post photos of my mods later. I going to do power off mod with reed switch.

Sergey
 

Offline Steps

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Re: UT61E Auto Power Off Modification
« Reply #43 on: February 08, 2016, 10:40:23 am »
A lot of water has passed under the bridge…
So, I did the mods of APO with reed switch. I guess it’s the easiest way (but not best,of course).
I fixed magnet to the box of data cable. Tried with neodymium magnet but unsuccessful (it would be more fancy with smaller and shiny), probably neodymium magnet too powerful for a reed switch. Any way you can see on the photo, its ok for me.
« Last Edit: February 08, 2016, 11:29:50 am by Steps »
Sergey
 

Offline Steps

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Re: UT61E Auto Power Off Modification
« Reply #44 on: February 08, 2016, 11:27:27 am »
And APO mod is useless without APO of the backlit. So I did APO of the backlight by transistor switch from pin pin 58 “SLEEP” (just as DeanA said above). So now the backlight switching off together with DMM.
I used red LEDs after I tried white one. Bright red LEDs have the same brightness at 10 mA like white at 2.5 mA. So white LEDs more energy effective to red.
Due to battery consumption is preferable to install bright white LEDs or orange.
You can compere backlit of UNI-T UT61E or FLUKE 17B+ on the attached photo.
And I going to do switching of the backlight by touch sensor https://www.eevblog.com/forum/testgear/uni-t-ut61e-backlight-mod-with-touch-sensor-(tutorial)/
Sergey
 


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