UNI-T UT61E Multimeter teardown photos.

[dr_p]

mine always initialises in 0.0000V (5 digits)

[hgg]

Strange. 
After initialization does it stay with 5 digits?

[mariush]

Same here, shows all 5 digits.

There are a couple or so undocumented features but they're documented in the IC datasheet (the IC used by the multimeter).

See the datasheet, from 3.1 forward, all kinds of things you can do in combination with the HOLD button : http://www.cyrustek.com.tw/spec/ES51922.pdf   

Plus there's a mention a few pages before saying if you keep hold pressed for 2 seconds while switching the meter on will keep all lcd segments lit until you hit hold again.

[Rick Law]

Mine switch on to 0.0000 Volt  (5 digits).  With test leads touching, it shows and stay 0.0000V.  When the leads are not touching, it will show random milli-volts as I move my body around which I assume to be it picking up static electricity and my body's field.

I am guessing: I suspect if it picks up the random static electricity over 2.2V it would go to and the range over 2.2V volt which would be 4 digits.

The biggest random volts I've seen is 0.1v (100mV) range, no where near switching to > 2.2V, but I can see it could happen if you are wearing wool and on carpeting.  I am not even sure if it will stay on that range after just a brief shot over 2.2V.

Rick

EDIT/Update:
I tried to reproduce a higher random voltage caused by static electricity on start up.  I used a 9v battery brushing by the test leads as it was powering up.  It went into the over 2.2v range reducing it to 4 digits (9.xxxx) for a brief moment.  But it settles back down to below 2.2V range displaying 0.0000 (5 digits).  So, at least for my version of firmware, my guess of brief static electricity causing it to change range is not on target.  Even if that happened, it came back down on its own.

[try]

Hi sdttn!

How did you suppress the original "Hold"-function?
Did you connect the the "Hold"-Pin to the "Range"-Pin?

How much current do you draw from BKOUT?
How do you know if this is just a logical output or an output that allows some current flowing?
I don't find any answer in the specsheet from Cyrustek.

Regards
try

Thanks for your reply.

By the way the DMM has not backlight function.
But the chip (ES51922) supports backlight function. The HOLD button is useless for me so I decided to use this button as backlight ON/OFF button.

[sdttn]

I just cut hold button trace.

[Lightages]

If you just cut the hold button trace and leave it disconnected, you loose the valuable feature of the delay hold. When you press the hold button for a few seconds the meter goes into a timed hold mode. During this time you can connect to the voltage you want to measure and then wait for the beep. At that time the meter will hold the value and you get almost the same benefit as an auto-hold like some Flukes have

[dr_p]

Also if you do the "photodiode-to-auto-power-off-from-RS232-handshake" hack you also lose the ability to wake up the meter from auto power off. It automatically wakes up in display HOLD, so you have to press the hold button to cancel that. If you switch ranges it goes to delay HOLD, so you'll have to turn it off, then on again via the rotary switch.


But you can maybe add a MCU and implement a dual function for the HOLD button: single press = backlight command, long press = delay HOLD. You lose the simple instant-display HOLD function, but that's useless anyway IMHO.


The auto-power off hack is the best bang for your buck, so to speak, because you lose no functionality of the meter. Only when you connect RS232 adapter, the meter disables serial communication and enables 15min auto power off.

[Lightages]

If Uni-T had not been cheap on the input protection, had configured the data cable for the auto power off switching, and supplied a USB cable instead, they could be sold for $75 and they would still sell like crazy. The backlight would be quite a bit more work to rework the design.

[T4P]

They already sell like hotcakes ... and no i don't mind the 50$ bracket. I rather they stayed there

[Rick Law]

If Uni-T had not been cheap on the input protection, had configured the data cable for the auto power off switching, and supplied a USB cable instead, they could be sold for $75 and they would still sell like crazy. The backlight would be quite a bit more work to rework the design.

Yeah, I would have like to see back-light and auto power off.  The USB v RS232 cable, I can see pluses on both sides.  But back  light and auto-power-off, I would have paid $10 for that two features.

Another nice feature I would like to have the rubber part of the housing a removable-hoster like construct similar to the Flukes.

What they should put out are:

>>  a 61E+ model.  $10 for that extra three features.
>> And a 61E+Super with BL/APO feature with 40,000 or 50,000 counts, max/min (with peak), better burden voltage for current measurement, 2Amp range.  220mA with a lousy burden voltage now is just too small (and burden voltage too high)  to be useful.
>>  And a 61E+Ultra with +Super, temperature, inductance, auto 6sec hold (as it is now) or steady-read then hold, and much better burden voltage for current.

[Legit-Design]

>>  a 61E+ model.  $10 for that extra three features.
>> And a 61E+Super with BL/APO feature with 40,000 or 50,000 counts, max/min (with peak), better burden voltage for current measurement, 2Amp range.  220mA with a lousy burden voltage now is just too small (and burden voltage too high)  to be useful.
>>  And a 61E+Ultra with +Super, temperature, inductance, auto 6sec hold (as it is now) or steady-read then hold, and much better burden voltage for current.

Get UT-61D,  you gain backlight, auto power-off, Superlow burden voltage (lowest resistance in Daves 100$ multimeter shootout), also cheap for around 50$ on ebay. Plus more multimeters is always priceless and enables to do alot more things. Even if you lose some resolution (maybe some accuracy too) you still have UT-61E to take care of those needs. Unless they come out with a multimeter with multiple isolated channels, those things are hard to beat when combined.

[iloveelectronics]

Get UT-61D,  you gain backlight, auto power-off, Superlow burden voltage (lowest resistance in Daves 100$ multimeter shootout), also cheap for around 50$ on ebay. Plus more multimeters is always priceless and enables to do alot more things. Even if you lose some resolution (maybe some accuracy too) you still have UT-61E to take care of those needs. Unless they come out with a multimeter with multiple isolated channels, those things are hard to beat when combined.

The main thing against all the other models (except E) in the UT61 series is how slow they are. Continuity and autorangong seem painfully slow on the A-D models.

[Rick Law]

...Plus more multimeters is always priceless and enables to do alot more things....Unless they come out with a multimeter with multiple isolated channels, those things are hard to beat when combined.

I am reasonably happy with the 61E.  I already have 3 others - 2 radioshack and a DT830B.  But I actually was thinking about getting a couple more  DT830B's when I was playing around with boost circuits:
In Volt, in current, out Volt, out current, drain current, that is 4 right there.  I could use another one to do adhoc readings.

One of my 4 is a DT830B, $6 DMM, not bad.  I use it as my volt meter for my PSU.  It actually performs better than the other cheapos from Radio Shack (4-8 years old).  So I was considering getting a pair of DT830B.  But I hate all those stuff on my table leaving me so little space.

I would not invest in another mid-low end DMMs.  If I would get more DMMs, I will probably aim for a higher end ones or real cheapies.  Mean time, I just got my ATMega328 as Volt/Current meter working on a breadboard and ordered parts to transfer it to PCB.  I divided up the 6 ADC's as 3 pairs of volt+current (switch-selectable) 0 - 5/15/30Volt and fixed 0-4Amp (using a 0.1ohm as current sense and amplified with OpAmp).  The two pairs I have working gets me +-1% to 4% accuracy.  Not bad when I have not yet calibrated them yet.  After I get the parts, I can get the 3rd pair working, transfer it to PCB, and then I'll do some software tricks (the ADC under-reads at low ranges).  If I can bring it closer to 1-2% using my UT61E as "accurate" reference, I just may end up using the ATMega as my PSU's volt+current.  All three channels shares common ground, so it took me a while to figure out how I would make that work for me.  If the thing works (at +- 1-2%), I don't need the DT830B's as volt/current meter.  If it doesn't, well, I learned a lot trying to get it working so far.

[don.r]

Just got the meter today from Franky. Thanks again, Franky! The autoranging is really slow, as noted above. The probes are... well... Uni-T probes... crap.  The meter really needs a backlight. Other than that, the display is crisp, the readings are accurate (when they get there) and getting 5 digits is great for less than $60.  Still waiting on my eBay UT136B for a nice comparison.

[Monkeh]

61E? Slow autoranging? It's pretty fast compared to most meters <$200.

[don.r]

61E? Slow autoranging? It's pretty fast compared to most meters <$200.

In ohms it seems to jump all over before settling down after 2 or 3 seconds. It could be the god-awful probes.  They really are bad. Like $10 meter bad.

[Monkeh]

61E? Slow autoranging? It's pretty fast compared to most meters <$200.

In ohms it seems to jump all over before settling down after 2 or 3 seconds. It could be the god-awful probes.  They really are bad. Like $10 meter bad.

Yes, the probes suck. This is known. Clean them.

[don.r]

61E? Slow autoranging? It's pretty fast compared to most meters <$200.

In ohms it seems to jump all over before settling down after 2 or 3 seconds. It could be the god-awful probes.  They really are bad. Like $10 meter bad.

Yes, the probes suck. This is known. Clean them.

I did clean them with IPA several times. I'll just use better probes. It seems to work fine with the Pomona's so its not the meter, just the probes making me think its the meter. 

[Lightages]

When cleaning the probes, you need to get a little aggressive. You can use chrome cleaner or Brasso. If you use isopropanol, then you should use fine steel wool to clean them. The plastic mold release and/or any plastic coating that might be there from molding the handles needs to be physically broken up to remove it. Do not use sand paper or abrasive pad as this will scratch and pit the plating on the probe tips and cause corrosion in the end.

[Brendan L]

How can a reading of less than zero ohms be achieved ?

[HKJ]

How can a reading of less than zero ohms be achieved ?

A DMM uses a constant current generator and measures the voltage across the resistor. Any external voltage will upset the reading, i.e. a negative external voltage will (usual) show negative ohms.
A few DMM's can compensate for small external voltages.

[T4P]

Apart from Agilent's magic volt bias canceller   
I certainly find that function very useful ... VERY USEFUL.

[PedroDaGr8]

In case anyone cares, I did a quick test hooking my "new" oscilloscope up to the ut61e. Below 200nF it uses a clear square wave. Above this, it registers no load so it shows nothing. I preceded to add a 2200uF "load" which shows a clear 1Hz pulse train

Sent from my EVO using Tapatalk 4

[cosmos]

The "new" scope picture looks like it came from a LeCroy 7200, a heavy power hungry beast sounding like a pair of 747s at takeof.
Turning off my 1kW electric oven and using the 7200 instead actually increased the room temperature.