Fnirsi -TC3

[fredo_]

Too lazy to post pictures, but my TC3 works perfectly with any resistor value between 4k and 6k.
My firmware is V0.3.
Tested with this resistor box :
.

[hud]

Today I received a new motherboard for TC3 and installed it into my TC2. In general it works properly, however, there are several strange bugs.
1. Generator. The output frequency is exact only in Square and Pulse modes, in other modes (sine, triangle, sawtooth) it's way off, up to 2%, and changes only in large steps.
2. Oscilloscope. On high voltage ranges (1 V/div and higher) in DC mode the zero line is off by 100..300 mV in a random direction (depending on the range), usually up. Can this be adjusted?
3. Oscilloscope. Low time per division ranges (5 μs/div and less) have incorrect X scale. For example, a 500 kHz wave on the 2 μs/div range must be EXACTLY 1 large box wide, actually I see 14..15 waves per 12 boxes. A 100 kHz wave on the same range must be 5 boxes wide, actually it's 4 boxes (is it 2.5 μs/div???). The 10 μs/div range seems to work properly.
4. Voltage. There is a calibration mode with two points: 5 V and 20 V. After calibrating (using AD584 for 5 V and a step-up converter for 20 V), it displays 5 V, 7.5 V and 10 V correctly (+/- 5 counts), but 2.5 V is 1% off (high). Why?

How did you calibrate the voltmeter? I couldn't find the menu to calibrate 5V and 20V ?

[TheDefpom]

I basic video doing some tests for ESR measurements:

🔴 A Surprising Result ? - FNIRSI DSO-TC3 ESR Measurement Testing - No.1273

[CaptainBucko]

I am observing the follow in resistors between 20k and 40k:
- 20.05kOhm resistor (OWON XDM1041) measuring 22.1kOhm (TC3)
- 33.11kOhm resistor (OWON XDM1041) measuring 35.2kOhm (TC3)
- 27.58kOhm resistor (OWON XDM1041) measuring 29.35kOhm (TC3)

while
- 684Ohm resistor (OWON XDM1041) measuring 690Ohm (TC3)
- 474.9kOhm resistor (OWON XDM1041) measuring 480.4kOhm (TC3)