Siglent Bench DMMs SDM3065X, SDM3055 and SDM3045X

[joeyjoejoe]

https://www.eevblog.com/forum/testgear/sdm3045x-versus-dm3058e-sensor-input-4-20ma/msg3793730/#msg3793730 and subsequent post. Can confirm there is no custom sensor option in the menu on my 3055.

[tautech]

https://www.eevblog.com/forum/testgear/sdm3045x-versus-dm3058e-sensor-input-4-20ma/msg3793730/#msg3793730 and subsequent post. Can confirm there is no custom sensor option in the menu on my 3055.

Great, thanks. Tomorrow Monday I'll go shaking trees to find out why 3055 don't have the custom sensor feature. 

[emilian]

@Dbldutch

I'm seeing weirdness about the LO terminal of my DMM as well. I have a Siglent 3065X-SC, still in the return window and I'm very disappointed with this finding.
I was not expecting the LO terminal to be grounded, let alone with a potential of 13.33V from the earth.
The 'HIGH' terminal also has a potential to the case.

This makes it impossible to use in a proper way in a working circuit which has signal generators and oscilloscope probing coupled.
I accidentally zapped an IC as well because of it. 

Is this normal? What do other users measure? 

Other than this issue the meter seems ok. I measured another isolated supply, batteries, etc.

[Kleinstein]

A DC voltage between ground and the LO terminal is indeed unusual. 13 V with the usual 10 M input resistance for the 2 nd DMM would be some 1 µA of current. It is normal to see some current there, but this is normally a AC current from capacitive current.  I don't know how well the Fluke DMM handles a large supper-imposed AC votlage in the DC ranges - the shown DC voltage may actully be an effect of the Fluke meter. It may be better to use the scope to measure the voltage. The interesting part would be more the AC part.

There could still be a weak point with the SDM3055 in a relatively with a large AC part.

[TheDefpom]

@Dbldutch

I'm seeing weirdness about the LO terminal of my DMM as well. I have a Siglent 3065X-SC, still in the return window and I'm very disappointed with this finding.
I was not expecting the LO terminal to be grounded, let alone with a potential of 13.33V from the earth.
The 'HIGH' terminal also has a potential to the case.

I think you are getting false readings from your Fluke, it may even be the fluke that is generating the voltages internally... I just tested my 3065X and got no voltage at all from either input jack and the meters ground, or the ground of any nearby oscilloscopes, I then tried to measure resistance in the same way, nothing, OL on my brymen 786, which means it is in excess of 60MOhm.

you could even be picking up EMI/RFI in the leads themselves which due to the lack of loading is generating a stray potential difference.

OR as you have the SC version, there could be some instrument connections on the scanner card causing stray voltages to be picked up.

[tautech]

A DC voltage between ground and the LO terminal is indeed unusual. 13 V with the usual 10 M input resistance for the 2 nd DMM would be some 1 µA of current. It is normal to see some current there, but this is normally a AC current from capacitive current.  I don't know how well the Fluke DMM handles a large supper-imposed AC votlage in the DC ranges - the shown DC voltage may actully be an effect of the Fluke meter. It may be better to use the scope to measure the voltage. The interesting part would be more the AC part.

There could still be a weak point with the SDM3055 in a relatively with a large AC part.

2V and under range is 10G.

[emilian]

Thank you for the quick replies. It's really helpful.
I must have a faulty unit with something shorting to the case.
I'll reach out to the seller for a fix.

- I took out the Scanner Card for the following measures just to confirm there's nothing wrong with it
- If I use Siglent DMM 3065X to measure its shell with the high lead, it reads 13.3V.
- If I measure DCV with Fluke meter from LO to shell I get 13.3V
- I used my scope to measure and I also get 13.3V from shell to LO
- If I change to ACV and measure the LO to shell (USB and case) with Fluke I get 14.8V
- If I measure current with Fluke from shell to LO I get some 60-70 mA
- If I power on shell to LO is some 16V.
- If I measure ohms with FLuke from shell to LO it grows as if it's charging a capacitor.

[bdunham7]

I'm seeing weirdness about the LO terminal of my DMM as well. I have a Siglent 3065X-SC, still in the return window and I'm very disappointed with this finding.
I was not expecting the LO terminal to be grounded, let alone with a potential of 13.33V from the earth.
The 'HIGH' terminal also has a potential to the case.

That looks like a problem to me.  Look at the polarity in the second photo.  What you appear to have is a low terminal that has about -20V potential with respect to ground, with an impedance of 5M or so.  This gives you the ~13V in the first photo, and then in the second photo you are not measuring an ~8.9V potential at the high terminal, you are seeing that potential from the low terminal divided by both 10M inputs of the two meters.

So the next step would be to use the current range on the 87V to measure from low to ground.  I'm assuming you'll see something on the order of 3-5uA.  It could be more or less because I only guessed at the numbers and the leakage could be nonlinear.

I'll reach out to the seller for a fix.

If you are in the return window, don't hesitate, send it back for a new one.

Edit:

If I measure current with Fluke from shell to LO I get some 60-70 mA

Yikes!  I was a bit off there, I guess.  Do you get the same if you measure from the ground shell of the BNC on the unit above, like in your first photo?

[Kleinstein]

This reallly looks like a broken unit. For the current measured to ground one could check  with the meter itself, but I woud not expect the fluke meter to be bad on this.

Getting some 13 V and quite some current looks like a linke to the raw supply some how, like a heat sink (e.g. the 5 V supply) touching the case or shield.
So this would be a unit to send back with a comment that it is very likely broken and not just send back for not wanting it.

[Bad_Driver]

I checked my SDM3065, it shows only some Microvolts against ground.
Your device is broken and you should ask for replacement.

Nevertheless: Merry Christmas to all readers, followers and Siglent club members!   

[Dbldutch]

I just measured my 3065X with a Fluke DMM from the + lead to Earth, and I measure 5.3VAC @50Hz and from the - lead to Earth 7.1VAC @ 50Hz.
In the DC mode of the Fluke, I measure only a few mV.

[Bad_Driver]

I have to come back to an early problem that was pointed out here some month ago.

I tried to get a fast reading of 4096 values with my SDM3065 (1 PLC, Auto-Zero, 2 VDC) for further FFT analysis.
With the help of TestController I can't achieve faster readings than 3/sec.

With reading to USB-stick I get up to 20 readings per second but the time deviation between the measurements is to big,
I used external trigger, with internal trigger it is much bader.

I assume fastest reading & storing will be with writing to internal memory, but there I get no time stamp (why? Siglent!!!!)
Has anyone find the best settings for this kind of measurements?

[HKJ]

With the help of TestController I can't achieve faster readings than 3/sec.

TestController can handle up to about 100 readings/second, but because it reads one value at a time meters will usually not work that fast with it.

For fast reading you need to disable auto-zero, when enabled the meter will need to do a two readings for each reading you request.
It is also a good idea to select manual range.

[Bad_Driver]

Hi HKJ,

thanks for your hints, but unfortunately it doesn't work for me. I tried all your advices but the limit is always about 6...7 readings per second.
The SDM is LAN-connected. I went down to 0.05 PLC, manual range 2VDC, no Auto-Zero but no chance to get faster readings.

B.D.
 

[HKJ]

thanks for your hints, but unfortunately it doesn't work for me. I tried all your advices but the limit is always about 6...7 readings per second.
The SDM is LAN-connected. I went down to 0.05 PLC, manual range 2VDC, no Auto-Zero but no chance to get faster readings.

I am not that surprised. On some meters you can do some sort of streaming captures, that may be a small program on the meter (New Keithley) or by capturing alternate buffers and then transmit them.
On some meters you can also decouple the capture and the reading of data (TC does that for some bench meters), this means you can get you table with stable timing, but the actual capture rate will not follow it.

On the keysight 34465/34470 TC can download the internal captured data and they can capture fairly fast (Keithley is faster, but TC cannot download data from them).

[Bad_Driver]

HKJ, you got it! As described earlier, I can do data capturing on USB-stick or internal.

Unfortunately the internal capturing provides no time stamp (shame on you SIGLENT!).
The external USB capturing has a time stamp but I wasn‘t able to get constant readings, there
are big time deviations from reading to reading. But I need a constant acquisition frequency for
following FFT. I Have to play a little more with external triggering.

btw: I exported the table of measurements to EXCEL and did there the FFT. Is a FFT function in Text Controller in future something you are considering?
The results beside the lower acquisition frequency were much better than with the USB-stick recording.

[HKJ]

btw: I exported the table of measurements to EXCEL and did there the FFT. Is a FFT function in Text Controller in future something you are considering?

It might very well be, maybe a popup window (or maybe in gridpanel) and a way to export both graphical representation and a table.
Note: It will not be spectrum analyzer grade readout, but a much more simple readout.

[oz2cpu]

two SDM 3055 side by side
ultra clean and stable 5V input
been like this for 7hrs straight
both brand new

Resolution, and Accuracy is not the same thing :-) no surprise
if I get access to another instrument, with 10 times the resolution and 10 times the accuracy
is there an easy way to tweek the numbers, so they read the correct value ?
or do i need special equipment, and special procedures to perform calibrations ?

[purpose]

Is there an easy way to tweak the numbers?

No, but here is all the info you'll need for your tweakery.

http://www.thedefpom.com/siglent_sdm_calibration.php

[bdunham7]

Resolution, and Accuracy is not the same thing :-) no surprise
if I get access to another instrument, with 10 times the resolution and 10 times the accuracy
is there an easy way to tweek the numbers, so they read the correct value ?
or do i need special equipment, and special procedures to perform calibrations ?

The specified tolerance for that instrument at 5 volts would be 16 counts.  Your two examples disagree by 4 counts.  Attempting to 'tweak' them is likely going to cause other issues--they'll disagree at different voltages (or temperatures)
or worse.  I doubt very much that you can improve on their operation with ad hoc methods.  Even official calibration by a certified laboratory may not improve things very much.  In any case, even if you want to attempt to improve them and can round up the equipment, you probably want to age them for a year or so first otherwise their initial drift may undo your tweaking calibration efforts.

[Bad_Driver]

Everyone wants to see such nice coincidence (photo) but this was only a lucky shot of me.

After a 500 h „burn in“ of the SDM3065 it settled down at 30…40 Microvolts  at 9.5 V beside my HP34401A.
And this is full in specs.
It‘s astonishing how good my old HP still is and also how good the SDM is (beside the other weaknesses).
I‘m pretty sure that the HP will do it another 20y, and we will see how the SDM will behave.

[2N3055]

two SDM 3055 side by side
ultra clean and stable 5V input
been like this for 7hrs straight
both brand new

Resolution, and Accuracy is not the same thing :-) no surprise
if I get access to another instrument, with 10 times the resolution and 10 times the accuracy
is there an easy way to tweek the numbers, so they read the correct value ?
or do i need special equipment, and special procedures to perform calibrations ?

That is about 80 ppm of difference. If you hypothesize one might be 40 ppm high and one 40 ppm low, they would still be in spec even for some 6.5 digit meters..
I wouldn't touch them. Also, like Bdunham7 nicely said, it would be prudent to wait for a year or two for them to settle.

And for end, a brain teaser: unplug them both and exchange their places: one from the top put on the bottom and vice versa.
Check again the voltages.. Are they the same? 

[CDN_Torsten]

It‘s astonishing how good my old HP still is and also how good the SDM is (beside the other weaknesses).
I‘m pretty sure that the HP will do it another 20y, and we will see how the SDM will behave.

I'm always impressed with how well the 34401A works. If I need a correct 'answer' this is the go-to DMM.  The K 181 is also quite good, but a bit more noisy.
I also have an SDM3055, but after 2 years of ownership...it's rarely used as I don't feel it produces quality results and I have to endure the fan noise...

[Bad_Driver]

Wow you got two 34401a!

My was about 300 Euro some years ago. Now prices are much to high (unbelievable). If  there has been another
favorable 34401a around, I had taken it and not the 3065.

But to be honest, beside the problems with the triggering and the slow read out/recording I like the SDM, the display is great, it is easy to use and it is warmed up much faster than the 34401a (15 min compared to 2…3h).
That is a benefit of the fan. But for 2 bucks more Siglent could choose more silent fan for their products.

I need only someone who explains to me how to get fast(er) readings with constant acquisition frequency out of it.
The data sheet claims 50 readings per second at 1 PLC, but I found no way to the get this readings „recorded“. Best case it is always about 5…7 readings with high time deviation from on reading to the other. I have to check this with the 34401a. 

[oz2cpu]

about the calibrations, I did look at this site

https://www.thedefpom.com/siglent_sdm_calibration.php

thanks a lot for the link, he is doing the same, adding a user cal, you can select to use or not,
I called my work, got ok to pick up our brand new calibrated 34465A and the two siglent are now passed 24hrs
the keyside is on 3 hrs, plan is to let them all run, for a few days to see what happens, i take date spamped pictures a few times pr day..
I also got a friend with a HP3458A he said i could just pop in and pick it up, in case i like to try play with some more digits.

anyways the defpom site contain good explain videos about the calibration, and how to use, and select the factory or the user cal,
so i figured i try play with this, at least just for fun, just this one range, just to see if I can make them all read the same,
i might learn a few things along the way, or at least had some fun playing with my stuff.

anyways : i dont have any luck with this, my SDM3055 just say bad file name, to the CVS file from that site,
so how to fix this ? any one tried his csv files, on a 3055 model ?

by the way : thanks for the info about specifications, and expected error, i was aware of this
like the defpom he also up perform his unit, quite a lot with this type of user calibration