new RIGOL DP832 1st channel LCD is wrong help!

[smile]

Hello, sorry for my bad English. RIGOL Puts certificates just because they can, not because the hardware complies to them IMO.

I have new RIGOL DP832, and first thing decided to check it. Upon boot you simply would discard the least significant digit in normal accuracy mode. But with High accuracy installed it seems to be way off from normal.

See attached LCD screen image, all 3 channels are set the same.
I connected digital multimeter Agilent U1252B that is more accurate than the RIGOL DP832, and all channels seem NORMAL.
Only LCD is showing wrong values for 1st channel.

Can I somehow correct it ? I would not want to sent the unit back, but I easily can because it's new out from the box I got today.
Thank you.

P.S. RIGOL has some quality issues, as up for a year there were no firmware updates, and calibration date on my is 2016-10-25, this is the same if I checked the calibration in the DP832 itself.

similar problem in year 2014

[Daruosha]

I believe your channel 1 is a bit out of calibration. If you have a 5-1/5 digits (the manual suggests 6-1/2 digits) multimeter, you can re-calibrate your channel 1 and fix it.

[smile]

I have the Agilent U1252B 4.5 digit DMM.

Question 1:
The voltage measured is subject to Load Regulation Rate ±(Output Percentage + Offset) + Linear Regulation Rate ±(Output Percentage + Offset)?

Or just the  Load Regulation Rate ±(Output Percentage + Offset)?


Question 2:

The SET and Displayed Voltage / Current should be displayes as +- 1mV / 1mA accurate or do I need to include Line and Load regulation? OR should I include  Programming + Display accuracy making it +- 2mV / 2mA?

I don't know why they specify Readback accuracy as this not measurable by any means since no external readback.

I did some measurements and will upload a table but I want to set the threshold right.

[rstofer]

I haven't hacked mine but when I set 30 mV on all three channels, the display reads 00.03V on Ch 1 & 2 and 0.03V on Ch 3.  Exactly what it should read.  The actual output is 31.4 mV on Ch 1 & Ch 2 and 30.7 mV on Ch 3.  So sayeth my Fluke 189 which was calibrated at the factory about 13 years ago.

[LaurentR]

I have the Agilent U1252B 4.5 digit DMM.

Question 1:
The voltage measured is subject to Load Regulation Rate ±(Output Percentage + Offset) + Linear Regulation Rate ±(Output Percentage + Offset)?

Or just the  Load Regulation Rate ±(Output Percentage + Offset)?


Question 2:

The SET and Displayed Voltage / Current should be displayes as +- 1mV / 1mA accurate or do I need to include Line and Load regulation? OR should I include  Programming + Display accuracy making it +- 2mV / 2mA?

I don't know why they specify Readback accuracy as this not measurable by any means since no external readback.

I did some measurements and will upload a table but I want to set the threshold right.

A few comments:
* The "high resolution" option only allows you to control the 1mV digit and read back to 1mV precision. No extra accuracy.
* In your accuracy calculation, the most important term is actually (from the datasheet):
"Annual Accuracy"
Ch1 V programming: 0.05% + 20mV
Ch1 V readback: 0.05% + 10mV

So your channel 1 may actually be in spec :-)

[smile]

I believe your channel 1 is a bit out of calibration. If you have a 5-1/5 digits (the manual suggests 6-1/2 digits) multimeter, you can re-calibrate your channel 1 and fix it.

Strange but the Keysight lists my DMM as (LCD 5 digits (50000)), not 4.5 as I thought would it work?
Is there easy way to reset the Rigol DP832 LCD CH1 zero mark back to zero? Because it seems it shows wrong, but output is not?

Now the stupid question, I know how to measure amperage, but:
Do you measure current by connecting a load like resistor or directly with multi meter as DP832 will limit the output?

[smile]

I have the Agilent U1252B 4.5 digit DMM.

Question 1:
The voltage measured is subject to Load Regulation Rate ±(Output Percentage + Offset) + Linear Regulation Rate ±(Output Percentage + Offset)?

Or just the  Load Regulation Rate ±(Output Percentage + Offset)?


Question 2:

The SET and Displayed Voltage / Current should be displayes as +- 1mV / 1mA accurate or do I need to include Line and Load regulation? OR should I include  Programming + Display accuracy making it +- 2mV / 2mA?

I don't know why they specify Readback accuracy as this not measurable by any means since no external readback.

I did some measurements and will upload a table but I want to set the threshold right.

A few comments:
* The "high resolution" option only allows you to control the 1mV digit and read back to 1mV precision. No extra accuracy.
* In your accuracy calculation, the most important term is actually (from the datasheet):
"Annual Accuracy"
Ch1 V programming: 0.05% + 20mV
Ch1 V readback: 0.05% + 10mV

So your channel 1 may actually be in spec :-)

You mean the threshold is to be calculated like "programming: 0.05% + 20mV" + "readback: 0.05% + 10mV"?
or just the programming: 0.05% + 20mV?

It's SET 1mV/1mA,  and 1mV/1mA  Display claims goes out the window then?

Having 15mA displayed (on LCD output seems OK) more on CH1 is strange non the less.

[H.O]

Strange but the Keysight lists my DMM as (LCD 5 digits (50000)), not 4.5 as I thought would it work?

Hmm, no, they list it as a a 4.5 digit, 50000 count meter.
Yes, there's 5 digits on the display but the most significant digit doesn't go 0-9, only 0-5 then it switches ranges so it's 4 "and a half" digit.

Regarding the DP832, if you program 1.00V or 10.00V what does your meter say and what does the LCD display say?

[Daruosha]

Once I said, your 1st channel might be a BIT out of cal, it could be within spec too. I cannot say much without enough information. Since I'm way too much obsessed with calibration of my instruments, i called your power supply out of spec. anyhow... prepare a list like below and tell us the SET figures and READ-BACK figures across full ranges on your channel 1:

set V   -  read V - DMM reading
1mV
10mv
0.1V
1V
10V
20V
30V

if your DMM is anything below 100,000 counts, don't mess-up with calibration of your power supply. Otherwise you can make it even worse.

[smile]

Once I said, your 1st channel might be a BIT out of cal, it could be within spec too. I cannot say much without enough information. Since I'm way too much obsessed with calibration of my instruments, i called your power supply out of spec. anyhow... prepare a list like below and tell us the SET figures and READ-BACK figures across full ranges on your channel 1:

set V   -  read V - DMM reading
1mV
10mv
0.1V
1V
10V
20V
30V

if your DMM is anything below 100,000 counts, don't mess-up with calibration of your power supply. Otherwise you can make it even worse.

SET V   -  Read Display V - DMM reading
1mV - 0.013V - 0.0027V  / 2.420mV on mv range
10mv - 0.022V - 0.0111V / 10.982mV on mv range
0.1V - 0.112V - 0.1017V   
1V - 1.012V - 1.0010V
10V - 10.012V - 10.001V
20V - 20.013V - 20.002V
30V - 30.011V - 30.001V

Isn't there simple way to set proper zero on CH1 on the LCD as voltage out is OK when I measure it. Other 2 channels are OK.

If not, then is it worth asking the dealer for another DP832 unit or ask them to ship this unit to RIGOL to calibrate this one properly?

[Daruosha]

Well, your actual output seems pretty good and well within the specs. But your read voltage is not as good as we expect.

You can calibrate the read back voltage on your channel 1 with your multimeter.  Go to the Test/Cal in the utility menu, enter the password (2012), select channel 1 and start VADC calibration procedure. However since your DMM resolution is not enough to meet the basic requirements suggested by Rigol,  i'd say try to borrow a dmm with minimum 200,000 counts and do the calibration steps, or take the risk and do it with your current dmm, but don't expect a big improvement. 

My personal suggestion is to be a bit patient and find a 6-1/2 digits dmm and calibrate it properly.

[smile]

In my country that means only metrology would have such multi meter, and that is in another city 200Km away.
The calibration would be manual and take allot of time and effort I believe.

Actually it's not worth price wise as nobody would agree to actually adjust the thing for decent price. And on new DP832 this is not right to begin with.

[mc3x]

Similar problem on my DP832, with CH1 ! only it outputs same wrong values measured as LCD shows.
It's brand new too. Seems RIGOL has quality control problems.

I however have installed the hi-res option code, and wonder what is common practice before sending it to distributor/RIGOL?

Should I uninstall the hi-res option? How? I read the codes are stored anyway so there is no point in unistalling them.
Has anyone been declared warranty void for installing hi-res option etc. by RIGOL?