RS-232 signal to NI 9401

[trevor34]

Hi,

I have a strain gauge torque sensor and I use a Peekel Picas amplifier to read the torque value.

I also have an NI 9401 which has eight digital input/output channels.

I would like to read the Picas torque value with the NI 9401 to use the values in Labview.

Since my DAQ can only read digital signals I intend to use either the Digital I/O or the RS-232 port on the Picas device (see attachment).

Can anyone tell me if this is possible and how I would have to make the connection?

Thanks a lot

[rolfk]

You can't use the 9401 to transmit RS-232 communication signals. And you can't possible transmit any meaningful torque values through those digital signals. Most likely the digital IO on your instrument is meant to control some 24 to 48 V relay or PLC input to activate when a certain pre-configured torque value has been exceeded.You definitely can't read the actual torque through that. The digital inputs are probably to have some safety switch or similar operation which will kill the torque.

[santo_13]

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@trevor34 wrote:

Hi,

I have a strain gauge torque sensor and I use a Peekel Picas amplifier to read the torque value.

I also have an NI 9401 which has eight digital input/output channels.

I would like to read the Picas torque value with the NI 9401 to use the values in Labview.

Since my DAQ can only read digital signals I intend to use either the Digital I/O or the RS-232 port on the Picas device (see attachment).

Can anyone tell me if this is possible and how I would have to make the connection?

Thanks a lot

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What do you intend to do with the torque reading?

You can skip the DAQ part and get a USB-RS232 adapter to directly read the values from the Picas device's RS-232 port.

[trevor34]

Thanks for the replies.

I am already using the NI 9401 to read a rotary encoder. I am processing the data in Labview, and I would like to add the torque readings from the Picas to Labview as well.

I thought it would be possible since the Picas has a 16 bit A/D converter, but I understand the digital signal can not be read easily by the NI 9401.

I also have an NI USB 6009 which I think can read the analog signal from the Picas. I will therefor try to use both NI's in my Labview, one for the digital encoder signal and the other for the analog torque sensor signal.

If I would use a RS232-USB adapter, can I read the signal with Labview? 

[santo_13 · Accepted solution]

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@trevor34 wrote:

If I would use a RS232-USB adapter, can I read the signal with Labview? 

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Yes, you can use the NI-VISA library to read from the COM port.

https://labviewwiki.org/wiki/VIWeek_2020/Proper_way_to_communicate_over_serial

[trevor34]

Thanks for the help so far. I am already successfully writing my encoder position as well as the derived velocity and acceleration using 'Write to measurement file'. I would like to add the torque data from the RS232 to this.

However, since the data from the RS232 is of type string, I am unable to do so. Is it possible to add this string data to the same Binary (TDMS) file?

I followed this tutorial: rs232 serial data acquisition using labview.

Similarly, I could use a 'Write to text file' to store the string data, but I would like to put everything into one file.

PS: If you have a look at my VI, can you also check why my Stop button only stops the encoder/DAQ assistant and not the entire while loop?