HT824 Calibration?

Taesungtech

Hello,

Yesterday I just received HT824 Process Calibrator.I tested HT824 and I found some accuracy issues.

Fluke 726 Precision Calibrator and Fluke 89 DVM was used for measurement. (Calibrated befor 8 months)

1. mV output accuracy test :
When set to 0mV output
- LCD backlight Off, DC adaptor disconnected : -0.088mV (0.098%) -> Not accptable
- LCD backlight Off, DC adaptor connected : -0.090mV (-0.1%) -> Not accptable
- LCD backlight On, DC adaptor disconnected : -0.017mV (0.019%)
- LCD backlight On, DC adaptor connected : -0.051mV (-0.057%)  -> acceptable

[size=13.3333px]When set to 10mV output
- LCD backlight Off, DC adaptor disconnected : 9.913mV (0.097%) -> Not accptable
- LCD backlight Off, DC adaptor connected : 9.909mV (0.101%) -> Not accptable
- LCD backlight On, DC adaptor disconnected : 9.981mV (0.02%)
- LCD backlight On, DC adaptor connected : 9.949mV (0.057%)  -> acceptable

When set to 90mV output
- LCD backlight Off, DC adaptor disconnected : 89.909mV (0.101%) -> Not accptable
- LCD backlight Off, DC adaptor connected : 89.909mV (0.101%) -> Not accptable
- LCD backlight On, DC adaptor disconnected : 89.987mV (0.014%)
- LCD backlight On, DC adaptor connected : 9.945mV (0.061%) -> Not accptable


2. RTD Ohm output accuracy test :
When set to 5.0ohm output (minimum of 5-400 ohm range)
- LCD backlight Off, DC adaptor disconnected : 4.93 (0.017%)
- LCD backlight Off, DC adaptor connected : 4.92 (0.02%)
- LCD backlight On, DC adaptor disconnected : 5.14 (0.035%)
- LCD backlight On, DC adaptor connected : 5.06 (0.015%)

When set to 400.0ohm output (maxium of 5-400 ohm range)
- LCD backlight Off, DC adaptor disconnected : 400.23 (0.057%) -> acceptable
- LCD backlight Off, DC adaptor connected : 400.22 (0.055%) -> acceptable
- LCD backlight On, DC adaptor disconnected : 400.62 (0.155%) -> Not accptable
- LCD backlight On, DC adaptor connected : 400.51 (0.127%) -> Not accptable

When set to 90mV output
- LCD backlight Off, DC adaptor disconnected : 89.909mV (0.101%)
- LCD backlight Off, DC adaptor connected : 89.909mV (0.101%)
- LCD backlight On, DC adaptor disconnected : 89.987mV (0.014%)
- LCD backlight On, DC adaptor connected : 9.945mV (0.061%)

3. Summary
- When using mV output : LCD backlight ON, DC adaptor disconnect
- When using RTD output : LCD backlight OFF, DC adaptor doesn't matter
- Does HANTEK have a plan for firmware update about this accuracy issues?
- If you have a plan, when?
- Is there a way for the user to calibrate HT824?

Taesungtech

CYH2018 replied at 2019-7-11 08:53
Dear sir,

Please do not connect DC adaptor when using, only use battery power.

Hello,

So, how do you explain the difference in accuracy between turning on the LCD backlight or turning it off?
Look at the results of my test shown above.
LCD backlight must be turned on for mV output, and LCD backlight must be turned off for RTD output to satisfy 0.05% accuracy.
And I don't think it's stipulated that you shouldn't use the DC adaptor.

Taesungtech

CYH2018 replied at 2019-7-17 13:19
Dear sir,

1) DC adaptor: This part of our design is flawed, and there are no plans for change.

Thank you for your efforts to improve the problem and look forward to the update as soon as possible.
Thanks again.