UT61E Auto Power Off Modification

[Legit-Design]

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.

[rolandpenplotter]

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.

[Wytnucls]

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.

[torr032]

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 ?

[Monkeh]

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.

[grumpydoc]

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.

[G7PSK]

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.

[torr032]

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.

[Monkeh]

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.

[dr_p]

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

from the Amprobe AM-270 user manual:

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.

[Monkeh]

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

from the Amprobe AM-270 user manual:

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?

[grumpydoc]

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.

[torr032]

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.

[Steps]

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?

[DeanA]

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.

[Steps]

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".

[DeanA]

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. 

[Steps]

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.

[Steps]

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.

[Steps]

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)/