I have an application where I need to feed the output of an op-amp working as a typical inverting amplifier to the recorder. The reason is because the actual voltage signal is in the range of 30-100 mV (a sensor). This is a completely DC circuit and the op-amp is only there to scale up the voltage on the sensor. When I measure the op-amp output with a multimeter everything works as expected. The voltage is in the range of volts (gain 100) and stable.
However, when I feed the same output to one of recorder’s channels the reading starts floating roughly between 0.3 V and 2.5 V literally in a matter seconds. I do realise there are input op-amps in the recorder itself so my question is: what would be helpful in order to chain them so that the voltage fed to the recorder’s DAC did not oscillate?
The external op-amp (TL072CP) works with a “traditional” dual supply voltage (+15V/-15V) and the sensor has its own power supply.
It seems there may be some 50 Hz “hum” at the output of the external amplifier.
Depending on the phase of the hum compared to the sampling of the PCS10, there will be seen the variation in the reading.
It is possible of course though, just for a test, I have replaced the sensor’s power supply with a battery once because any 50 Hz hum started there would be extra amplified. It has limited the floating a little but not a lot (which would point to the op-amp as another culprit). Besides, the reading looking like I described - it’s floating randomly but only occasionally does it look like an oscillation. It certainly is bound within min and max level. I’ll take an extra look at dampening any hum coming from the power supplies. As for the sampling rate of the PCS10 - is there any way to limit it? To be honest I don’t necessarily need 100 S/s but the PCLab application seems to only let you control the scaling of the graph, not the actual sampling rate. Even 10 or 1 S/s would be fine. Like I said, it really is a DC kind of application (monitoring).
[quote=“mimir”]As for the sampling rate of the PCS10 - is there any way to limit it? To be honest I don’t necessarily need 100 S/s but the PCLab application seems to only let you control the scaling of the graph, not the actual sampling rate. Even 10 or 1 S/s would be fine.[/quote]The sample rate is not fixed 100 S/s, but it is “tied” to the selected Time/Div. setting.
Only at the highest speed (1 s/Div) the sample rate is 100 S/s.
On all other ranges the sample rate is slower e.g on the 100 s/Div range it is 1 S/s.
You’ll see the sample rate on the right top corner of the waveform screen.
[quote=“VEL255”][quote=“mimir”]As for the sampling rate of the PCS10 - is there any way to limit it? To be honest I don’t necessarily need 100 S/s but the PCLab application seems to only let you control the scaling of the graph, not the actual sampling rate. Even 10 or 1 S/s would be fine.[/quote]The sample rate is not fixed 100 S/s, but it is “tied” to the selected Time/Div. setting.
Only at the highest speed (1 s/Div) the sample rate is 100 S/s.
On all other ranges the sample rate is slower e.g on the 100 s/Div range it is 1 S/s.
You’ll see the sample rate on the right top corner of the waveform screen.[/quote]
Yes, scratch that question. I’ve seen the scale changing but neglected to notice the sampling rate is also different. Sorry about the noise.