Data Logger Communication Errors with RS232 Interface

The problem could be the setup of the customer, or it could be a Microsoft problem (see below).

I have seen setup problems cause communication errors -- these are things to check with customer:

1.  Did customer "add" 34970A to IO Libraries under Serial interface (COM1, COM2, etc)?

2.  After step 1, make certain ALL of the settings on the 34970 are the same on the IO Libraries -- Parity, Stop bits, etc.  *** Be especially careful of FLOW CONTROL setting.

3.  If FLOW CONTROL is not the same, it will appear that instrument can send and receive commands well -- UNTIL user presses the Scan button or when data is attempted to be taken out of the instrument.  This is because for small messages, there is no need for a handshake because the buffer is large enough to hold the answer in a single transaction.  When asking for hundreds of bytes of data (or more), the buffer will fill, and at that point the handshake of Flow Control will be needed to assure that the sender does not over run the receiver with data it is not ready to receive.  The FLOW CONTROL setting must be the same on both the IO Libraries and on the 34970A.  I usually use XON/XOFF.

4.  The BAUD RATE can make problem number 3 worse.  If customer still has a problem, have him use 1200 baud.  At this speed, he may even be able to use Flow Control of NONE because data moves slowly enough that the receiver can keep up with the data send speed.  If it works at this low speed, you can try higher speeds.

5.  In none of the above are the problem, the problem can be the computer.  Newer computers do not support hardware handshake properly.  See the two links below:


Why is there data being dropped or missing from the 34970A when uploading scan data?
 http://www.home.agilent.com/agilent/redirector.jspx?action=ref&cname=AGILENT_FAQ&ckey=457237&lc=eng&cc=US&nfr=-11143.0.00
 
Problems Using RS-232 on Agilent Instruments with Laptop PCs running any Microsoft OS
 http://www.home.agilent.com/agilent/redirector.jspx?action=ref&cc=US&lc=eng&ckey=131609&cname=AGILENT_EDITORIAL

I hope his problem does not turn out to be number 5, because we cannot solve this Microsoft problem.