Electrical – Retrieving data from Agilent 34401A Digital Multimeter over the RS232 interface

multimeterrs232scpi

I want to interface Agilent 34401A Digital Multimeter over the RS232 interface. The settings (baud rate, parity, number of start and stop bits) are set to be same on multimeter, pc (device manager) and on the application that I use for terminal. Programming language is SCPI.

I successfully control the multimeter, that is I execute the commands such as: syst:rem; :meas:volt:dc? 10, 0.003; :conf:volt:dc 10, 0.003; :sens:volt:dc:rang 100; but I get no response over RS232 interface from my multimeter.

For example when I execute the command :meas:volt:dc? 10, 0.003; the measurement is performed and the voltage is displayed on multimeter’s display, but the value is not sent over RS232 to my terminal. No response what so ever.

In the manual for the multimeter there is a statement after each command — “bus enter statement". Relevant extract provided below.

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I could not find any reference or explanation what is meant by this.
Does a special command exist for retrieving data from the multimeter?

:read? makes no effect on the multimeter.

Useful hint for someone who is also trying to set up RS232 communication with this device: Even if in the manual the colon preceding the SCIP command is not given, the multimeter returns “unknows header” error if it is not present.

Best Answer

The problem was in the way I send a command over terminal. After a command the multimeter expects line feed character, in PuTTY this is <ctrl-j>.

The code below successfully gets response with a value of a voltage. 

syst:rem; 
:meas:volt:dc? 10, 0.003;
<ctrl-j>

I found solution reading through this forum question: https://www.eevblog.com/forum/testgear/34401a-serial-interface-problems/

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