Sanwa EM7000 Analog Meter and Uni-T UT71D problem

[nukie]

Hello,
I finally got my long awaited Sanwa EM7000 FET analag meter, direct from the Japan factory. Here's a mini review I wish to contribute. I have very little experience with these meter. After testing and comparing it to a Fluke 189 with superior DC averaging function, I would say don't bother with it unless you are like me after some nostalgic memories of playing with my dad's Sanwa meter when I was a kid. The Fluke 189 totally demolish the analog meter at square wave DC 10Hz and above, advantage for it's digital readability.

The analog meter wins for anything under 10Hz but it starts to swing quite a bit when it gets down to 3Hz. The Fluke 189 produces rock stable reading that matches the analog meter, for any duty cycle percentage above 10Hz. No cheap DMM I have come close to this performance. This test puts a smile on my face, prior to this, I have no idea such performance exists in this Fluke.

I also pitted my Uni-T UT71D against the two, it does quite badly and I also found a weird flaw. Unlike the 189, it will only provide a stable reading starting from 50Hz which results matches the 189. Frequency between  1-49Hz is just some random digits jumping around. When frequency is increased to 51Hz it starts jumping around like a poker machine again, sometimes it is stable but very inaccurate. Once the frequency is raised to 100Hz everything becomes normal again. So the DC measurement is good for 50Hz, 100Hz, 150Hz, 200Hz... and so on. This goes on until 10KHz or so. Beyong 10KHz it's stable and accurate again. Hmm... if you have a Uni-T please do a test like that I did. The duty cycle of the square wave does not matter much. Sometimes the UT71D shows stable reading but the result is incorrect. When it's back to multiples of 50Hz again the result is correct.









Spare fuse, and spare fuse holders



Simple piece of device.



Toshiba N-Channel Fets

[MrPlacid]

On my cheap analog meter, I found out that the red probe turns negative and the black probe turns positive when it's in resistance mode. I am curious if the Sanwa does that too.

[nukie]

Yes it does, about -3.29v in the low ranges then drops to about -2.8v for x100.

[MrPlacid]

Thanks, for the reply and the great review with lots of beautiful pictures.

Looking at the inside, I can tell that's no cheap multimeter. Those aren't cheap looking fuses and there is also a spare fuse inside! (I see lots of Sanwa immitations on ebay like Samwa, Sunwa, or Sanwu.) If it were chinese fake, those fuses would be cheap fuses and without a spare.

Comparing yours and my cheap "sunwa" imitation, I can tell yours is way better. Yours is a NULL meter, has power on indicator, and an on/off switch. I think mine will be sitting in a corner collecting dust, but it serve it's purpose and got the analog, nostalgic itch off of me.

I hope you find many great uses with your analog meter!

[zaoka]

Is it accurate when testing DC voltage and ohms?

[alm]

I also pitted my Uni-T UT71D against the two, it does quite badly and I also found a weird flaw. Unlike the 189, it will only provide a stable reading starting from 50Hz which results matches the 189. Frequency between  1-49Hz is just some random digits jumping around. When frequency is increased to 51Hz it starts jumping around like a poker machine again, sometimes it is stable but very inaccurate. Once the frequency is raised to 100Hz everything becomes normal again. So the DC measurement is good for 50Hz, 100Hz, 150Hz, 200Hz... and so on. This goes on until 10KHz or so. Beyong 10KHz it's stable and accurate again. Hmm... if you have a Uni-T please do a test like that I did. The duty cycle of the square wave does not matter much. Sometimes the UT71D shows stable reading but the result is incorrect. When it's back to multiples of 50Hz again the result is correct.

This sounds quite normal to me. If you check the normal mode rejection ratio specs (if they spec it), it usually states that the figure is only for 50/60Hz +/- 0.1% or so. The trick is to use an integration time which is a multiple of the line frequency. That way you average out the inevitable mains noise that's present in many signals.

This trick doesn't work if the frequency is significantly off, hence the difference between 50Hz and 51Hz. I would expect it either to also work at 60Hz or to be switchable between 50Hz and 60Hz. Unless they have different models for different regions (unlikely) or just don't bother making it work at 60Hz.

[saturation]

Nice.  Thanks for sharing, wonder photos and write up.  I haven't seen the guts of an analog MM recently manufactured, I wonder who still uses those?  Some observations.

• Its looks like a lot of hand soldering in Sanwa PCB
• Quality workmanship for a hand job
• There is no 'made in japan' written anywhere

Your comments on UT71D are shared by other reviews on eevblog on different functions, it should ring a cautious word to folks who buy them.  There is a good story by a Brazilian eevblog poster using it to monitor VDC and seeing its accuracy is not what is written on the spec sheet, compared to his existing DMMs. 

I still have my original YX360 Sanwa AMM, its over 30+ years old and a real made in japan item, I use it as a general output voltage monitor.  Since its entirely passive and uses no batteries except for the ohms range, I can leave it on all day, day after day.

[saturation]

If you don't mind, I noticed in this photo on the left, you have what looks like an HP/ Agilent 3610 or thereabouts, analog PSU, is this right?  Its peaking behind the Uni-T DMM.

If so, can you mini review it for us, what do you think of its stability?  Can you dial down to under 1VDC, and under 100mA and still have stable output?  How low an output can you dial it down before the output becomes too erratic?

[nukie]

Is it accurate when testing DC voltage and ohms?

Yes surprisingly linear but it's not easy to read you have to be looking at the meter right angle to be able to read the result. Please look at the spec sheet for accuracy.

I would expect it either to also work at 60Hz or to be switchable between 50Hz and 60Hz. Unless they have different models for different regions (unlikely) or just don't bother making it work at 60Hz.

I took time to test it at 60Hz this time at 30%, 50% & 90% duty square wave. Fluke 189 is showing a stable 2.9546v, the Uni-T UT71D is switching between 2.7xxx and 3.0106. At 50Hz both showing 2.9549v. I went to my friend's place and we tried his FG, same results. This is also same for triangle wave.

• There is no 'made in japan' written anywhere

I still have my original YX360 Sanwa AMM, its over 30+ years old and a real made in japan item, I use it as a general output voltage monitor.  Since its entirely passive and uses no batteries except for the ohms range, I can leave it on all day, day after day.

It's made in Japan. Sorry I should have shown more pictures. Unfortunately this unit won't work without batteries.

If you don't mind, I noticed in this photo on the left, you have what looks like an HP/ Agilent 3610 or thereabouts, analog PSU, is this right?

You are right it's a E3610A. I will start a new review thread on the power supply. It's a versatile unit for electronics engineering. I like the small size of it, and love it for being linear. It's quite old so the caps started to leak and corrode the pcb tracks . Fortunately my nose was sensitive enough to pickup the cat urine smell. They are now replaced with Panasonic FM and FC caps, I don't know if this changes the performance because it was working surprisingly fine when the caps was leaking!!

[/URL]
I also have a Philips PM2811 60W programmable switching power supply. It's a medium boat anchor. Love these Dutch made products very good engineering. I will post some internals pics if anyone is interested. Oh btw, the Hakko mod is also really cool, been wanting to share it, guess it's time to make lots of post.

[Bored@Work]

Yes surprisingly linear but it's not easy to read you have to be looking at the meter right angle to be able to read the result. Please look at the spec sheet for accuracy.

This is what the mirror on the scale is for. It is not for decoration bling bling

You correct your viewing angle until the pointer hides its own image in the mirror. This limits the parallax error during reading. This is absolutely essential and standard procedure when working with an analog meter.

Of course, when having to do mandatory lab exercises during my studies a common way of cheating was to use the parallax error. You calculated the theoretical values in advance. And during the lab you looked at the, of course analog, meter from varying angles, until you had a reading that matched the theoretical value +/- some error. When then asked if you really did measure that value you could wholeheartedly confirm that you did see that value on the scale