Why is my HI 2160RC always in REC mode when changing set points?

When sending the command to set a rate and start the system, the HI 2160RC rate controller drops into REC mode until it can collect new rate data for this new rate. This is true even if the rate being sent is unchanged and regardless of what communications protocol is used. This process initializes the rate exception routine and sets the controller output percentage (OP%) to a rate defined by the rate table. This causes a delay of two ROC time base settings and any averages defined. 

This is not the case in the HI 4060.  In the HI4060 the rate changes set over communications, in any mode, is a percentage of the rate as calculated and monitors the actual rate in the automatic mode.  The HI 4060 does not drop back to volumetric mode.   You may make changes at will and have a smooth transition for each change.

Rate changes for the HI 2160RC series can only be sent over communications in the STOP condition.  Sending rate changes in the RUN mode can corrupt the controller.  To send a rate change during production.  Send the initial set rate with the START command.  If a change is required, send a ABORT command, followed by the START command with the new rate, and then send the command again with the remote function section as zeros. (start, abort enable section)

The proper way to send the command is to send it once and then make the word two equal to zero and resend the Command once again, and stop sending the command. (Word two defines the remote functions.)  The HI 4060 is more straight forward and does not require a strict regiment of command.

The HI 2160RC setup command should only be sent when there is a rate change or system status. (START, STOP, PAUSE)  Sending the start, stop or pause command continuously will keep the controller in a constant REC condition.

If your HI 2160RC application requires constant rate corrections, more often than every two minutes, then the Remote Set point option would be a better option selection. You can run the Remote set point option and a communications card in the same system using the expander option box.

Remote set point is a standard feature in the HI4060 and is used for ratio control to track wild flows.  The rate set point maybe changed only from the remote set point when enabled.

The HI2160RC+ is still supported for repairs.  The HI2160RCs are no longer supported due to the lack of parts availability. 

Conversion to the HI 4060 rate controllers should be in your plans.