Products > Test Equipment
Rigol DP832 - Firmware list and bugs
Armxnian:
Anyone else have the bigger display read higher than the smaller display? Mine reads 4mV higher than what is set for many voltages. Even set at 0v, the big displays shows .004. Some voltages like 11v show the same reading. My multimeter shows I'm getting what I set it to. It's quite annoying that the big displays is higher, makes it a bit useless. I'm on the latest version and have the higher resolution enabled.
H.O:
What do you mean with "the big and small display"?
On the main user interface the numbers at the bottom displays what you've got it set to and the larger number in the middle of the screen is what the metering circuit in the supply measures the actual voltage at the output terminals to. Try shorting out the supply, the set voltage stays at whatever while the actual voltage goes to zero, or very close to it.
--- Quote ---It's quite annoying that the big displays is higher, makes it a bit useless.
--- End quote ---
If they were to display the exact same value all the time it would either have to actually BE the same value (ie either the set value OR the actual value) and THEN it would be useless and a waste of screen real estate or the internal circuitry would have to be extremely accurate so that the actual output voltage always matched the set output voltage down to the least significant digit. A 4mV difference between the set value and the readback value is well within its specifications (which is 0.05%+20mV on the set voltage and 0.05%+10mV on the readback).
Oh, and the high resoultion option means you can set the output voltage in 1mV increments (instead of 10mV increments). It doesn't mean that the absolute accuracy of the actual output voltage OR of readback circuitry is increased.
If you still think it's useless, put a piece of electrical tape over it.... ;)
Then again, perhaps I completely misunderstodd what you meant by bigger and smaller display in which case you can simply disregard the above.
Armxnian:
You understood correctly, and all your points are true in regards to the hardware. I just thought it was some weird software bug that offset the reading by +4mV since it was present on almost every setting, even with the output set at 0. But further testing today confirms other values, like +2,3,4,5,6mV at different settings, so everything is functioning correctly.
LaurentR:
--- Quote from: Armxnian on April 23, 2015, 03:03:53 pm ---You understood correctly, and all your points are true in regards to the hardware. I just thought it was some weird software bug that offset the reading by +4mV since it was present on almost every setting, even with the output set at 0. But further testing today confirms other values, like +2,3,4,5,6mV at different settings, so everything is functioning correctly.
--- End quote ---
For some data on the DP832 DAC and ADC, see this thread:
https://www.eevblog.com/forum/testgear/noob-dac-linearity-in-the-dp832/
The bottom line is that the DAC has a resolution of about 0.5mV. Its linearity across the range is not great and varies strangely (from -5mV to +10mV, see the graphs), even after calibration. There is a noticeable temperature coefficient. The ADC is entirely separate (thus the discrepancy on the display between the DAC setting and the ADC readout) and seems to be much more precise and accurate (more or less +/- 1mV across the range).
If you have access to a good bench DMM, you can recalibrate your DP832 yourself (see the first post of this thread). But you'll still see the readout vary by +/- 10mV across the range.
broderp:
--- Quote from: Armxnian on April 23, 2015, 06:51:28 am ---Anyone else have the bigger display read higher than the smaller display? Mine reads 4mV higher than what is set for many voltages. Even set at 0v, the big displays shows .004. Some voltages like 11v show the same reading. My multimeter shows I'm getting what I set it to. It's quite annoying that the big displays is higher, makes it a bit useless. I'm on the latest version and have the higher resolution enabled.
--- End quote ---
Normal. (As others have posted) I'm following this thread and links and just wonder how much more it would have cost ROGOL to incorporate some sort of feed back to compensate for the voltage drift and attempt to 'regulate' it to match the set display. Maybe they do and this is the best it can do? :-//
My unit (no hi-res option) when powering up to the DEFAULT mode shows CH1 & CH2 at 00.01V and CH3 is dead on at 00.00V. It does appear to fluctuate somewhat, but I believe it's still within spec. Under load it may not match the set point, but as long as its solid and doesn't change significant, I'm OK.
Either way, for my needs its fine.
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