Hello,
I am having some weird problems with the PT-104, which reminded me a bit of this older post topic23701.html
As a setup, I have only tried it in USB mode so far, and I use it for reading 3 different devices with mV and V output differentially, with the mV devices being attached to channel 1 and 4, and V device to channel 3.
When doing this, the logger only reads channel 3 constantly. Both mV channels mostly show 0V. With the Picolog Recorder under Windows, and with a Python code under Raspberry Pi / Raspbian.
The weirdness starts that I sometimes get a reading of one of the mV channels. Sometimes I can trigger this when changing the acquisition setting. In Python, the returned status is always OK.
So my questions are rather:
- Could it be that the PT-104 is not fit for measuring mV and V signals?
- Could it be an issue with usb instead of LAN communication? (I have not tried that yet)
- Should there be default time delays between measurements? (I already tried this, but anyways)
- Could it be that the input channel resistance is too low when the acquisition is triggered, that a current flow interrupts the voltage measurement?
- Could it be a defective component?
For completeness, here is the Python code for the RasPi as I couldn't find it in the archive yet:
The USB PT-104 should be suitable for differential voltage measurements up to 2.5 V.
When you refer to using a time delay, have you tried a 720 ms delay (this is the time taken to convert a single reading).
It might be useful to see a diagram/photo of the setup and which connection pins on the input are being used. You can post this here or send it to support@picotech.com
Have you tried a multimeter to measure the voltage as well for reference purposes?
I use the screw terminal adapters, so pin 4 (the outermost) is connected to ground, and the differential voltage is between pins 2 and 3 (with 4 being positive).
Here's a picture:
Multimeter Readings between 3 and 2 show the correct voltage. Plugging the screw terminal into the PT-104 is a bit cumbersome, but it was executed correctly. It is only the voltage acquisition itself.
720 ms sounds overly long to me, but I will try this.
Should the time delay be between 2 UsbPt104GetValue commands?
750 ms delay did not change anything, unfortunately.
It is pretty difficult to connect the device with the internet now, so I haven't performed the driver update yet. What's the date of the driver, what is its name?
Because I installed the system only about 2 months ago.
I still have the same problem with the mV mode. But the voltage mode works without problems.
So: mydll.UsbPt104SetChannel(handlePointer,1,5,2) does not work properly, while mydll.UsbPt104SetChannel(handlePointer,1,6,2) works.
What's the difference between libusbpt104.so and libusbpt104.so.2, by the way?
libusbpt104.so is a symbolic link to the shared library libusbpt104.so.2 , which means that code does not need to change if the version of the library changes.
Can you post your code as it is now, we need to see where you have delays, as you will need 720ms between a SetChannel and GetValue call to read sensible data for a single channel.