6890 remote connection

I am setting up our 6890 to work with an old ATD400 and need some assistance with communications.

The ATD400 wants a contact closure to know the GC is ready, and provides a contact closure to start the Run. So far so good.

A pic of the ATD400 manual is provided below.

According to Agilent doc A15844 - 6890 REMOTE CABLE PIN OUT, the GC takes that contact closure between GND and "START", pins 1&3, I hooked up the RS232 cable we have, which has three pins taken, 1, 3 and 7, supposedly all you need. I checked the remote start by manually providing the contact closure between pins 1&3, and it does start the run. In addition, when i start a Run via Chemstation and it waits for injection, I do see a contact between pins 1&7, aka the GC "Ready" contact closure signal ... so that is as expected as well. It is not there, aka 4 MOhm resistance when the GC is NOT ready.

Could somebody (Agilent GC applications engineer?) please confirm that these are the standards i should expect?

Before a run is commencing, voltage between pins 1&3 is 3 V, curious. Is that also correct (seem like the standard used to 5 V 20 years ago?) ?  Shortening that connection does start the run as expected, see above.

However, when I make the connections as per the ATD400 manual (cables and pins as per instructions on the page posted below), the communication does not work, aka the ATD does not seem to observe the GC Ready, and thus it does not send a contact closure to start the run. It rather remains in "ready" mode waiting for the GC to be ready ...

I feel like I need to install a resistor somewhere ... I am very sure this is an "old" issue, would love to hear how it was solved.

  • btw, the ATD400 does show 5 V on its GC Ready connection, pins 20&13 on the above shown manual page. Shortening that -- as in contact closure -- with a simple bridge does make the ATD start the injection. So the question is whether the relay inside the 6890 is just mismatched with this contact closure requirement (meaning the 5 V potential on this old instrument is not liked by the 6890?)

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