2408: Can no longer set 'Target Setpoint' to '0' ?

Eurotherm 2408: Have permissions on Target Setpoint parameter changed?

We have integrated 20+ 2408 modules into our systems and have previously implemented "OFF" by setting the Target Setpoint (Modbus 2) to '0' and then setting Instrument Mode (Modbus 199) to "Standby (1)".

On a newly-purchased 2408, the device rejects the '0' target setpoint with an "Illegal data value" response (3).

Has something changed in the 2408 programming that isn't reflected in the firmware version displayed at startup?
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  • Hello Phil. There have been no firmware changes to the 2400 series controllers for many years. The current version has both parameters and are unchanged in their address, function or permissions level. What version of firmware are your previous controllers?
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  • On powerup they report "4.11".

    We switched to the Eurotherm controllers about two years ago and have had the same "turn off" sequence in place for the entire time. This new one is the first of the 2408's we've received that throws an error when attempting to set the Target Setpoint to '0'.

    Are there any conditions involving other parameters that are used to validate data for the Target Setpoint? Perhaps this one unit was not 100% at factory defaults when we received it and something unexpected is interfering?
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  • Hello Phil,

    If you have only used them for the last 2 years then the firmware will be the same as your older units. Do you have a clone file for the older instruments? It would be easier to load that and try it out again. Have you managed to establish that the communications port is actually working?
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  • No, I do not have a clone file, but I could give it a shot. Our application assumes a default "stock" set of parameters and (at connection time) configures the non-stock settings we require.

    The port works perfectly well - our application connects, configures and monitors the 2408 reliably until it's time to shut off our the heaters at which point it errors out on trying to set a '0' setpoint.

    If we swap in a different 2408 module then things work as we expect but the issue reappears as soon as we've gone back to the original module.

    Again: is there any parameters that affect whether and what a user is allowed to write into the Temperature Setpoint parameter?
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  • Hi Phil. There are no parameters that I can think of that should affect writing to the Target SP parameter. It is a writable parameter and there are no permissions settings with this or any other parameter that could change this. The only thing I can think of is that the setpoint limits have been set for a low limit that is greater than 0. You could check this through the front panel by going into Full mode and checking the SP high and low limits in the SP list. Taking a clone file using our Itools software would also enable you to look at this and compare to your other controllers.
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