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# Measuring Voltage up to 4 decimal places using TDS3032 Oscilloscope

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#### Tahsinhossain

##### Newbie level 5
Hi Everybody,

I am trying to capture waveform data from TDS 3032 oscilloscope through RS232 port. All samples have 1 decimal place data only (i.e. 20.3V) whereas I need something like 20.2985V. Is there any way to get 4 decimal places from oscilloscope?

I really appreciate any help.

Tahsina

That's hardly possible with 9 Bit vertical resolution.

Basically I have a sense resistor (0.156ohm) at an inverter output. I am using two probes to acquire voltage level before and after the sense resistor so that I can deduct one from another to get the voltage drop across the sense resistor. The objective is to find inverter output current. However, since I am getting only one decimal place, the two probes are giving something like 19.5V and 19.4V but this is not giving me proper voltage drop. According to my theoretical calculation, the inverter output current is 62mA, which means there should be 0.009672V drop across the sense resistor. I hope I could explain my problem to you.

Can you suggest any alternative to solve my problem?

The oscilloscope only has 9 bits of vertical resolution. That is 512 levels.

To measure a voltage of .0001V, your maximum voltage (voltage range) would be at best .0512V, far below the 20V range you are measuring.

Set the inputs to A-B, this will get your 9 bits to work on the difference of the two signals. Just check that you are not exceeding the dynamic range of the input amplifiers.
Frank

FvM

### FvM

Points: 2
Set the inputs to A-B, this will get your 9 bits to work on the difference of the two signals.
Not sure about. With most DSO that I know, A-B is a digital operation rather than utilizing an analog differential amplifier.

I suggest you get some gain before the probes, like a
fast enough instrumentation amplifier (if there is one that
you deem fast enough). Since you are limited in full scale
resolution, get to full scale early.

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