Canadian Tire Mastercraft DMM New and old revision teardown

[macboy]

This meter is on sale again for ~$30 CDN (regular $70). With the currently low $CDN, this is an especially attractive deal.

The manual ranging meter also mentioned in this thread is on for ~$20 (regular $60). I wouldn't recommend that one, it is only 1999 count (vs 6200), has limited capacitance measurement (20 uF vs 60000 uF), limited frequency measurement (20 kHz vs >50 MHz), and judging by the teardown posted in this thread, it is calibrated by several adjustment pots (i.e. calibration accuracy is poor and it will drift). The $30 meter is electronically calibrated (constants stored in an EEPROM) so it will drift much less. In my opinion, though the manual range meter is cheaper, it is not as good of a deal.

[l0rd_hex]

Bonus points if you buy it all in Canadian Tire 'Money'

[macboy]

Using information from the UNI-T UT210E thread, I made some modifications to my Mastercraft:

• Increased full-scale counts to 8000 count instead of 6000 (auto-range up at 8001, down at 750)
• Added 80.00 mV and 800.0 mV ranges for AC and DC volt (auto-ranging) (press Select to toggle AC/DC)
• Added ability to switch between AC and DC voltage measurement without changing the rotary switch (press Select to toggle AC/DC)
• Added ability to switch between degree C and F without changing the rotary switch (press Select to toggle C/F)
• Ability to change the auto-off and backlight timeout to suit the user.

Just the mV ranges themselves are a fantastic upgrade. The extra counts are a bonus. The AC/DC and C/F switching will come in handy I'm sure, since it's easier to press the Select button than to rotate the switch, which is generally a two-handed operation.

In order to add the mV range, I needed to "steal" the Ohms switch position. I moved the Ohms (and diode and continuity) measurements to the CAP switch position; you press Select to change to the desired function. I have mine set to the following sequence: Resistance -> Capacitance -> Diode -> Continuity -> (repeat)...

The mV range has a resolution of 10 microvolts, and and input impedance of >500M on DC (higher than the 11M or 10M input impedance for other ranges) and 10M on AC. It is surprisingly accurate and noise-free. The "normal" AC and DC functions also have a 800.0 mV range which is manually selectable with the range button (it won't auto-range down below 8.000 V range). That is different than the mV-specific ranges: it has a 10M input impedance and a few digits of noise (AC) or offset (DC) with a shorted input. The operator needs to use care with using the mV ranges, the input protection is not as good as in the other voltage ranges. In the higher voltage ranges, the input goes through a 10M resistor before seeing anything else. In the mV ranges, the input is set up the same as in the Ohm or Cap measurement functions. The overload protection is via a PTC and a pair of transistors designed to conduct beyond a certain voltage, causing the PTC to rise in resistance to help protect to meter. If you connect a high voltage, high energy input like AC mains to the input in mV (or Ohm or Cap) mode, be prepared to suffer the consequences of at best a damaged meter, and at worst... explosion and injury.

The counts are limited to 8000 due to the need for AC measurements to have extra headroom. It seems the chip's ADC works up to around 12000 counts or so. For DC, we could use 9999 counts, but if you tried to use that for AC, the waveform would clip (a 9.999 V_RMS sinusoid has a peak value around 14.141 V, beyond ADC full-scale), resulting in a displayed value less than actual. Setting the limit of 8000 counts gives enough headroom for accurate measurement of a sinusoidal signal. If the AC input signal has a higher crest factor, like a triangle wave, or noise, then one should consider manually ranging down, in order to ensure ADC headroom to capture the higher peaks. This is a limitation common to all sampling-type RMS AC meters. The original 6000 count full-scale resolution accounts for a crest factor of >2.0 at full-scale, which is quite good enough. The 8000 counts reduces the margin but is a compromise to gain extra resolution.

I was not able to add RS-232 output, as the required I/O pin is being used for something else.

I will post the technical details later, including how to customize your own meter if you don't like my way. All you need is a programmer that can read/write a 24C02 I2C EEPROM, and a suitable soldering equipment and skills to either remove/replace the SOIC package or solder fly-wires.

edit: corrected input impedance for DCmV

[Paul Moir]

 
The more I use this meter the more it's grown on me despite it's faults.  DC mV will be a very welcome addition!
 

[macboy]

Here are the technical details of the modifications that I described above.

The meter has a 24C02 EEPROM in SOIC package. This has 256 bytes of data which includes some configuration and some calibration data. I modified specific parts of the configuration without changing calibration data. It is important that you understand that you must read your EEPROM data, then modify only the specific bytes for these changes; the other data must remain intact. If you simply copy my EEPROM, you will ruin your calibration.

For the reason above I will not post a binary of my EEPROM, only an image of the changes to be made. Attached is a screen capture showing the data in my EEPROM with all changed bytes in RED.

Address 0x10,0x11 is the nominal full scale, changed to 8000 (0x1F40), note the byte swap for all two-byte data values.
Address 0x12,0x13 is the range-up value, changed to 8001 (0x1F41).
Address 0x14,0x15 is the range-down value, changed to 750 (0x02EE).
The rationale for choosing 8000 as full-scale is explained in the previous post.

Addresses 0x80-0xBF configure the various switch positions. There are 16 possible switch positions (not all are used for this meter), and 4 possible functions for each switch position. The switch positions are labeled in the attached image of the meter. The attached chart shows the data to place in a memory location to enable the associated function.

Note that 0x80, 0x90, 0xA0, 0xB0 control the four functions for switch position 0, so 0x81, 0x91, 0xA1, 0xB1 control the four functions for position 1, etc. On this meter, there are 11 switch positions (plus "OFF" which doesn't count). You can see that the "ACV" position is shown as "9" which means that the four memory locations for functions under that position are 0x89, 0x99, 0xA9, and 0xB9. Looking at the data dump, you can see 0x89=0x06 and 0x99=0x05. This means the first function is ACVmV and the second is DCVmV. 0xA9 and 0xB9 are zero which means no function. So setting the switch to "ACV" and pressing "Select" will toggle between the ACV and DCV measuring functions.

Address 0xFB is the automatic power off in minutes. 0xFC is the backlight off timer in seconds. Set either to zero to disable.

To facilitate easy repeated modifications, I removed the EEPROM, then attached a DIP socket to the pads with short lead wires. I soldered another 24C02 EEPROM into a SOIC-to-DIP adapter board, so that I can easily remove it to program it in the TL866, then place it back in the socket.

[Paul Moir]

Ah, I finally got a chance to start playing with it today.  I enabled the 8000 count thank you very much, and played around a bit with the range switch.  Something I really like in a multimeter is separate diode and continuity settings rather than the select button.  Since I only rarely use the cap or frequency settings I hijacked them.  The frequency setting has an inherent duty cycle secondary function which causes an interesting fault: once you switch into it you cannot switch out.  You're stuck switching between frequency and duty cycle until you change the rotary switch.   

I made the degF position the DCmV/ACmV position.  At first I thought this was a mistake since it makes you use the mA/uA jack instead of the V jack, since the thermocouple adapter fits there.  But in retrospect, I think I like it that way.  It reminds me that the mV range isn't as well protected and also the probe will likely not be there when high voltages are present.

Trying to make the DCmV position a secondary function of DC or ACmV secondary to AC gets you a ErrE error.

I played around a bit with the RS-232 but I couldn't get it to enable.  Like you (macboy) said, the pin is being used for the incorrect jack warning.  I had hoped that could be at least disabled when using data out, or even better mapped to one of the LEDs.

[macboy]

Ah, I finally got a chance to start playing with it today.  I enabled the 8000 count thank you very much, and played around a bit with the range switch.  Something I really like in a multimeter is separate diode and continuity settings rather than the select button.  Since I only rarely use the cap or frequency settings I hijacked them.  The frequency setting has an inherent duty cycle secondary function which causes an interesting fault: once you switch into it you cannot switch out.  You're stuck switching between frequency and duty cycle until you change the rotary switch.   

I made the degF position the DCmV/ACmV position.  At first I thought this was a mistake since it makes you use the mA/uA jack instead of the V jack, since the thermocouple adapter fits there.  But in retrospect, I think I like it that way.  It reminds me that the mV range isn't as well protected and also the probe will likely not be there when high voltages are present.

Interesting.

Trying to make the DCmV position a secondary function of DC or ACmV secondary to AC gets you a ErrE error.

Yes, it won't work because the required internal connections are not the same at all. There are DCV and ACV functions that have a mV range (and alternate DCV and ACV functions that do not). These are not the same as the strict mV function which is high input impedance.

I played around a bit with the RS-232 but I couldn't get it to enable.  Like you (macboy) said, the pin is being used for the incorrect jack warning.  I had hoped that could be at least disabled when using data out, or even better mapped to one of the LEDs.

No hope for RS-232 I think. Oh well.

You can't arbitrarily assign functions to different rotary switch positions. The rotary switch does indeed change some internal connections required for different types of measurements. The Cap function can't be put onto the Hz/Duty switch positions (not if you expect it to work anyway) since the internal connections are not the same. The Cap, Resistance, Continuity, Diode, and mV functions use the same internal connections which is why I hijacked the Ohms position for mV on my meter. I moved the Ohms (and other) functions to the Cap switch position. The Hz/Duty has unique connections and can't do anything else. The connections required for each function are detailed in table 11.3 on page 11, and if you look at the example schematics you can see those connections in the circuit.

Interestingly, both Volts and Amps measurements use the same connections (all connections open) so it may be possible to put V and A measurements on the same switch position. You could wire up the meter to measure both A and V since they use different terminals and switch between them at the push of a button. That could be useful.

[Paul Moir]

Ah, that must be the original Chinese datasheet.   I've only been looking at Kenny Wong's translation.  I'm having some software issues with it going all grey when I mouse over it.  Ah Flash, when will you finally die?  Ignorantly clicking random links on a Chinese website hasn't gotten me very far, but it has been entertaining!

I tried out putting voltage on the current ranges and that works just fine, except as expected the meter howls at you for having a probe in the wrong jack.  But it's a simple matter to back the probes out a hair or just use unshrouded probes for this very handy function.  It's definitely going into my meter; I'm just sitting on the fence about deleting the AC ranges for mA and uA to make it even more handy.

Oh, the "halo" described by HammerJoe way back is caused by residual stresses in the plastic cover from when they molded it.  You can use polarized light and filters to visualize them.  The polarized light from a LCD monitor is a handy source, and naturally there's a filter on the multimeter's LCD screen.

[julian1]

I agree with Dave that the sweet spot is to own 4 DMMs, so you can measure current and voltage in and out of your circuit all at the same time.

I'm wondering if a 34970A with the multiplexor option wouldn't be a simpler strategy?

[user99]

I saw Crappy Tire put them back on sale so I grabbed one.  Another happy customer, hard to beat for $30.   
It's spot on according to my 3478a in the volt ranges. 

Now to read up on the calibration.  I added the mV ranges to the TempF switch but both AC and DC mv range is out about 1mV. 

Thanks for the tutorial!   

[mstoer]

I picked up one of these as well.  I have 3 hand held meters now and one benchtop.    My first meter (bought around 20 years ago) is a Wavetek DM16XL   it cost around $140 at the time and this Mastercraft puts it to shame for only $30.  Not only that, it runs on 2 AAA NiH rechargeables, so no more running around for 9V batteries. 

Marcell

[SkyMaster]

Canadian Tire could sell quality DMM and still make a profit, but Canadian Tire decided to sell bottom of the barrel quality DMM in order to make even more profit.

You should actually try one before condemning it.  ...

So I did buy one, several months ago.

Bonus points if you buy it all in Canadian Tire 'Money'

And I paid it all with Canadian Tire Money. The DMM 052-0052-2 was on sale at 60% off.

I returned it for exchange, as the first one I bought had a crack in one of the plastic tubes that are over the banana jack. The second one had a crooked display, but this was fixed by re-positioning the display LCD.

The test leads are not pretty. But I have to admit that for $30 CAD plus sale taxes; this is a very good buy.


Canadian Tire now also sell the "Mastercraft 5-in-1 Digital Multimeter" 052-1899-2. The particularity of this DMM is that it also measure sound level, illumination, and humidity. Regular price is $80 CAD. This multimeter appears to be identical to the All-Sun EM5510.

 

[Regis]

I bought this multimeter in 60% off sale as SkyMaster.

However, the k-type thermocouple cannot be found anywhere. It is discontinued.

I'm a newbie in multimeter. Can I buy any k-type themocouple for this multimeter?

[jesuscf]

I bought this multimeter in 60% off sale as SkyMaster.

However, the k-type thermocouple cannot be found anywhere. It is discontinued.

I'm a newbie in multimeter. Can I buy any k-type themocouple for this multimeter?

Yes, but...  Check

https://www.eevblog.com/forum/testgear/canadian-tire-mastercraft-dmm-new-and-old-revision-teardown/msg876419/#msg876419

The only catch is that the multimeter is not designed to accept the standard k-type thermocouple connector.  This can be easily solved with a couple of inexpensive standard banana plugs.

[SkyMaster]

I bought this multimeter in 60% off sale as SkyMaster.

However, the k-type thermocouple cannot be found anywhere. It is discontinued.

I'm a newbie in multimeter. Can I buy any k-type themocouple for this multimeter?

Hi Regis,

Any type-K thermocouple should work.

But there is a small issue; on the 052-0052-3 DMM, the spacing between banana jacks are not 0.75 inch. Most thermocouple (for DMM) come with banana plugs with a 0.75 inch spacing. You may need to find a type-k thermocouple with individual banana plugs.

 

[The_Dsigner]

Just saw Canadian Tire added another meter to their lineup but in the Maximum line.

http://www.canadiantire.ca/en/pdp/maximum-digital-multimeter-with-true-rms-0521898p.html#srp

[SkyMaster]

Just saw Canadian Tire added another meter to their lineup but in the Maximum line.

http://www.canadiantire.ca/en/pdp/maximum-digital-multimeter-with-true-rms-0521898p.html#srp

This newly introduced DMM #052-1898-4 seems to be a slightly modified Mastech MS8250D; except for the Function and Back-light buttons and small differences with the rubber holster, this look like a Mastech MS8250D

Mastech MS8250D - http://www.p-mastech.com/product/detail/355

The_Dsigner, your assignation for this week, is to find out if this new Canadian Tire DMM has a two lines LCD display and a USB interface.

 

[Tachyon]

Having recently bought the latest iteration of this DMM ( 052-055-6 ), I was happy to stumble across this thread. If this hard hitting, no quarter given crew can let this thing off as easy as they have here, I'll be more than happy with it. Given there are a lot of us hobbyists that don't need and or don't want to spend on brand names like Fluke, it's a big deal to find something that meets the "good enough" standard that is all we need.

I got mine on one of the sales mentioned too for like $25 CAD and am very happy with it so far. I wanted to just put in my two cents regarding the latest iteration of this device. One thing that impresses me is that it appears they've listened to the feedback and made some positive changes based on the more common complaints. For example, the battery compartment is improved and has much better fit and finish, no longer seeming like they hacked in a AA box into a 9v compartment feel. Also, the backlight is now on it's own button from the data hold so that button dance has been eliminated.
Overall, the fit and finish and general quality of this device is better than 9 out of 10 of the non-professional DMM's I've owned. The exception being an older Radio Shack DMM I've had for years that has a nicer fit and finish, but is definitely a bench model and not up to any sort of rugged field use. This Mastercraft model sits in between. Sure, it wouldn't likely last iong used hard in the field every day, but I'm certainly not afraid to take it out of the house/shop either. The leads are decent and flexible in the cold. The LED indicator for the plug ins is a nice touch. The display is large and very readable and the backlight is bright. The range of features is more than most non professionals will ever need and certainly more features than I could ever afford to replicate with an equivalent Fluke model. Most importantly the testing I've seen puts it in the "more than good enough" category accuracy wise and that's the most important thing IMO anyway.

Frankly it seems like the killer bang for the buck option for hobbyists and non professionals and even as a secondary device for pros that have Flukes with only basic feature sets that they occasionally need to supplement.

[Silveruser]

Just a note, meters are again on sale for the next week.  I picked up one of the newer ones with light meter, RH meter, sound meter. I'll try and start a new theard with pictures soon.

George

[macboy]

The "052-0052-2" model number has been recycled yet again. I had noticed perhaps a month ago that stock of this multimeter quickly disappeared from shelves shortly after the most recent sale. Now we now why, they've replaced it. This new third model has similar specs, but looks completely different yet again. Without testing one in-hand it is impossible to say what the real specs and features really are; as noted here, the specs for the 2nd model were completely wrong (reused from the first model). They still are re-using the same specs including note of a "transistor test" which only the 1st model had, the 2nd and now 3rd models don't. The display is now significantly smaller, which is really too bad, as the large-digit display of the 2nd model was a great feature.

Link:
http://www.canadiantire.ca/en/pdp/autoranging-digital-multimeter-0520052p.html

[jesuscf]

I saw this new multimeter on sale yesterday. Two thing I didn't like off the bat compared to the 'previous' model: no DC current and no temperature.

The "052-0052-2" model number has been recycled yet again. I had noticed perhaps a month ago that stock of this multimeter quickly disappeared from shelves shortly after the most recent sale. Now we now why, they've replaced it. This new third model has similar specs, but looks completely different yet again. Without testing one in-hand it is impossible to say what the real specs and features really are; as noted here, the specs for the 2nd model were completely wrong (reused from the first model). They still are re-using the same specs including note of a "transistor test" which only the 1st model had, the 2nd and now 3rd models don't. The display is now significantly smaller, which is really too bad, as the large-digit display of the 2nd model was a great feature.

[SeanB]

They got a new container load or three back in stock, and keeping the same SKU makes it easier for the shops inventory wise, as they probably only cost under $1 each when shipped.

[retiredcaps]

Two thing I didn't like off the bat compared to the 'previous' model: no DC current and no temperature.

The picture of the latest version has DC current mode.

[jesuscf]

Two thing I didn't like off the bat compared to the 'previous' model: no DC current and no temperature.

The picture of the latest version has DC current mode.

Ooops!  You are right: it has DC current mode.  I need new glasses...

[SkyMaster]

Two thing I didn't like off the bat compared to the 'previous' model: no DC current and no temperature.

The picture of the latest version has DC current mode.

Ooops!  You are right: it has DC current mode.  I need new glasses...

But the combined input jack for mA, uA and everything else; this is really a step back. Especially when the previous version had "input jack alert" when the lead was inserted in the wrong jack.