Products > Test Equipment
Siglent SPD3303X-E Hi-Resolution Output Unlock?
mawyatt:
--- Quote from: TheDefpom on July 16, 2021, 08:09:09 am ---My experience doing this kind of cal stuff with gear is that sometimes they don’t actually use a “0” cal point, but something other than 0, it sounds like you should be loading the unit up with 100mA and then doing that part of the cal so it sets its 100mA point when it is actually supplying 100mA, and then moving on from there.
I haven’t read the cal procedure for these units, but from what you have written I am 99% sure that is what is wrong.
--- End quote ---
The cal procedure should fit a simple straight line fit, or Y=MX+B. Per manual the two fits are at 100ma and 2.5A. The CC 100ma offset is not exactly 100ma, more like 85ma on ch1 and 90ma on ch2, and 115ma on ch1 and 122ma on ch2 in the other unit. On the 3303X that is good (I'm not about to try and calibrate it!!) this is a really good fit on both voltage and current, within +-1ma or +-1mv over the entire range as measured with our KS34465A!! The CC setting are also spot on over the entire range, as you would expect with almost 0 offset. Think Siglent is using 24 bit delta-sigma ADC and DAC (kind used for electronic weight scales), so some real precision here!! We've used this 3303X as a variable reference on many occasions, it's accurate, stable and low noise, sure it's not a precision calibration reference but when you need say 1.250V, 2.500V, or 5.000V this puppy is spot on! So hat's off to Siglent for using this kind of ADC and DAC!!
However, the other two 3303X have not been able to get the CC offset back to around 0 where it should be like the one mentioned above.
Many may not care about the current limit CC setting and just set it above some arbitrary limit, as long as the voltage & current readings are accurate. However in our use, especially when dealing with expensive semiconductors in a development system, having a precise CC or current limit can help protect things from overcurrent. I've used this method for over 40 years when we had very accurate current limit lab supplies (HP, Lambda and others), and this has saved the day often!!
Have another SPD3303X-E arriving 7/17, and debating whether to try and "enhance" it to a 3303X, if we do don't think I'll try a cal procedure just yet. If I find some time today will try fiddling with this some more on the unit that's hosed up.
I'm wondering if somehow "enhancing" a 3303X-E to a 3303X has something to do with this, as I'm sure the factory or others would have run across the CC offset problem, or maybe it's bug in the latest firmware release related to the "enhancement". Was able to convert back to a 3303X-E from an enhanced 3303X on one unit, but the offset remained and still could not be removed, so getting back to the initial state of the 3303X-E has failed.
Best,
mawyatt:
--- Quote from: TheDefpom on July 16, 2021, 08:24:33 am ---Ok, I am reading the service manual right now…
Shown for Ch1, change channel to Ch.2 once ch1 done.
This sets the 100mA cal point: CALibration:CURRent ch1,3,NR3 (with NR3 being the actual current present with the load set to 100mA)
This sets the 2.5A cal point: CALibration:CURRent ch1,4,NR3 (with NR3 being the actual current present with the load set to 2.5A)
It is a bit confusing in the manual where it also has a DISPLAYING calibration section too, which is basically identical apart from the ch1,3 being ch1,1 and ch1,4, being ch1,2 instead.
--- End quote ---
Agree, this is a bit confusing and takes some time to figure out what this cal procedure is trying to do. You have a "Display" value for voltage & current and a "Setting" value for both. This is how I think it's working, the Display value is what's being measured by the internal ADC, for Setting value it's what's being produced by the internal DAC. When you do a calibration for voltage the output Setting is what you set, 1 or 25 volts per manual, then you enter the DMM actual reading in the CALibration:VOLTage command. With two Settings of 1volt and 25 volts, the Y=MX+B equation is fit which matches the Setting and Display values to the entered DMM readings.
When you do a calibration for current the output Setting is what you set on the EXTERNAL LOAD, 100ma or 2.5 amps per manual, then you enter the DMM actual current reading in the CALibration:CURRent command. With two LOAD Settings of 100ma and 2.5A, the Y=MX+B equation is fit which matches the Display & Setting values to the entered DMM readings.
A little algebra shows Y1=M*X1+B and Y2=M*X2+B, so M=(Y2-Y1)/X2-X1) and should yield ~1. B= [Y1+Y2 -M(X1+X2)]/2 which should be ~0 since X1+X2 ~ Y1+Y2 and M~1.
When you do a voltage cal, the Current must be set to higher than the load current which is just the DMM, anything above ~10ma should work. When you do a current cal the Voltage must be set to something higher than the DMM & Load voltage requirement, usually greater than a few volts is sufficient.
Best,
2N3055:
--- Quote from: mawyatt on July 16, 2021, 05:41:00 pm ---
--- Quote from: TheDefpom on July 16, 2021, 08:24:33 am ---Ok, I am reading the service manual right now…
Shown for Ch1, change channel to Ch.2 once ch1 done.
This sets the 100mA cal point: CALibration:CURRent ch1,3,NR3 (with NR3 being the actual current present with the load set to 100mA)
This sets the 2.5A cal point: CALibration:CURRent ch1,4,NR3 (with NR3 being the actual current present with the load set to 2.5A)
It is a bit confusing in the manual where it also has a DISPLAYING calibration section too, which is basically identical apart from the ch1,3 being ch1,1 and ch1,4, being ch1,2 instead.
--- End quote ---
Agree, this is a bit confusing and takes some time to figure out what this cal procedure is trying to do. You have a "Display" value for voltage & current and a "Setting" value for both. This is how I think it's working, the Display value is what's being measured by the internal ADC, for Setting value it's what's being produced by the internal DAC. When you do a calibration for voltage the output Setting is what you set, 1 or 25 volts per manual, then you enter the DMM actual reading in the CALibration:VOLTage command. With two Settings of 1volt and 25 volts, the Y=MX+B equation is fit which matches the Setting and Display values to the entered DMM readings.
When you do a calibration for current the output Setting is what you set on the EXTERNAL LOAD, 100ma or 2.5 amps per manual, then you enter the DMM actual current reading in the CALibration:CURRent command. With two LOAD Settings of 100ma and 2.5A, the Y=MX+B equation is fit which matches the Display & Setting values to the entered DMM readings.
A little algebra shows Y1=M*X1+B and Y2=M*X2+B, so M=(Y2-Y1)/X2-X1) and should yield ~1. B= [Y1+Y2 -M(X1+X2)]/2 which should be ~0 since X1+X2 ~ Y1+Y2 and M~1.
When you do a voltage cal, the Current must be set to higher than the load current which is just the DMM, anything above ~10ma should work. When you do a current cal the Voltage must be set to something higher than the DMM & Load voltage requirement, usually greater than a few volts is sufficient.
Best,
--- End quote ---
Mike,
I believe that is the error.
Procedure is to calibrate 4 points: 100 mA and 2.5A for current set and readout, as you said.
But external load is set for 3A constant all the time. You set the PSU for 100 mA and 2.5A points and measure with external meter.
Load set at 3A could probably be replaced with dead short, but this way you have safe, current limited short that you know won't overload PSU even if calibration is completely off..
I don't have the PSU, but could you try this way?
Connect output to load. Set load to CC 3A (this is constant trough all 4 measurements)
(Calibration of readout of 100mA point)
Set PSU voltage to 10v, set current to 100mA
Measure current with external meter.
CALibration:CURRent ch1,1,"measured current"
(Calibration of readout of 2.5 A point)
Set PSU for 2.5A
Measure current with external meter.
CALibration:CURRent ch1,2,"measured current"
(Calibration of current limit of 100mA point)
Set PSU voltage to 10v, set current to 100mA
Measure current with external meter.
CALibration:CURRent ch1,3,"measured current"
(Calibration of current limit of 2.5 A point)
Set PSU for 2.5A
Measure current with external meter.
CALibration:CURRent ch1,4,"measured current"
And that for both channels.
If I'm right, i might write down the procedure in clearer language and submit it to Siglent..
Regards,
Siniša
mawyatt:
--- Quote from: 2N3055 on July 16, 2021, 08:07:18 pm ---
--- Quote from: mawyatt on July 16, 2021, 05:41:00 pm ---
--- Quote from: TheDefpom on July 16, 2021, 08:24:33 am ---Ok, I am reading the service manual right now…
Shown for Ch1, change channel to Ch.2 once ch1 done.
This sets the 100mA cal point: CALibration:CURRent ch1,3,NR3 (with NR3 being the actual current present with the load set to 100mA)
This sets the 2.5A cal point: CALibration:CURRent ch1,4,NR3 (with NR3 being the actual current present with the load set to 2.5A)
It is a bit confusing in the manual where it also has a DISPLAYING calibration section too, which is basically identical apart from the ch1,3 being ch1,1 and ch1,4, being ch1,2 instead.
--- End quote ---
Agree, this is a bit confusing and takes some time to figure out what this cal procedure is trying to do. You have a "Display" value for voltage & current and a "Setting" value for both. This is how I think it's working, the Display value is what's being measured by the internal ADC, for Setting value it's what's being produced by the internal DAC. When you do a calibration for voltage the output Setting is what you set, 1 or 25 volts per manual, then you enter the DMM actual reading in the CALibration:VOLTage command. With two Settings of 1volt and 25 volts, the Y=MX+B equation is fit which matches the Setting and Display values to the entered DMM readings.
When you do a calibration for current the output Setting is what you set on the EXTERNAL LOAD, 100ma or 2.5 amps per manual, then you enter the DMM actual current reading in the CALibration:CURRent command. With two LOAD Settings of 100ma and 2.5A, the Y=MX+B equation is fit which matches the Display & Setting values to the entered DMM readings.
A little algebra shows Y1=M*X1+B and Y2=M*X2+B, so M=(Y2-Y1)/X2-X1) and should yield ~1. B= [Y1+Y2 -M(X1+X2)]/2 which should be ~0 since X1+X2 ~ Y1+Y2 and M~1.
When you do a voltage cal, the Current must be set to higher than the load current which is just the DMM, anything above ~10ma should work. When you do a current cal the Voltage must be set to something higher than the DMM & Load voltage requirement, usually greater than a few volts is sufficient.
Best,
--- End quote ---
Mike,
I believe that is the error.
Procedure is to calibrate 4 points: 100 mA and 2.5A for current set and readout, as you said.
But external load is set for 3A constant all the time. You set the PSU for 100 mA and 2.5A points and measure with external meter.
Load set at 3A could probably be replaced with dead short, but this way you have safe, current limited short that you know won't overload PSU even if calibration is completely off..
I don't have the PSU, but could you try this way?
Connect output to load. Set load to CC 3A (this is constant trough all 4 measurements)
(Calibration of readout of 100mA point)
Set PSU voltage to 10v, set current to 100mA
Measure current with external meter.
CALibration:CURRent ch1,1,"measured current"
(Calibration of readout of 2.5 A point)
Set PSU for 2.5A
Measure current with external meter.
CALibration:CURRent ch1,2,"measured current"
(Calibration of current limit of 100mA point)
Set PSU voltage to 10v, set current to 100mA
Measure current with external meter.
CALibration:CURRent ch1,3,"measured current"
(Calibration of current limit of 2.5 A point)
Set PSU for 2.5A
Measure current with external meter.
CALibration:CURRent ch1,4,"measured current"
And that for both channels.
If I'm right, i might write down the procedure in clearer language and submit it to Siglent..
Regards,
Siniša
--- End quote ---
Reading the procedure again it does read as you indicate, thanks for pointing that out. However following this path of setting the load to 3A and using the 3303X Current setting for 0.1 and 2.5 amps for the calibration points still does not remove the current offset. Just tried this 4 times, and reset the current reading and settings a couple times, then the calibration procedure keeping the load at 3A, then issued a complete coefficient reset with the *CALCLS 8 command a couple times and went thru the same current calibration procedure a couple times. Results are the current offset remains intact, nothing seems to affect it!!
BTW either using the load as the current control, or the 3303X current setting, results in the same excellent current reading throughout the range from a few ma all the way to 3.2 amps, accurate with +-1ma!! Just wish I could figure out how to get rid of this !@#$ current offset, this has become a real pain!!
Thanks for spotting this,
Best,
blurpy:
Did you try this procedure on the unit you converted back to X-E as well?
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