Quikeval LTC2983 -999 measurements

I cant get the quikeval program with LTC2983 to stop giving me -999 measurements. It worked in January with the Demo Circuit 2210A for measurement of a PT-1000 resistor with a 2000k Ohm Rsense. Now we have manual wiring to the reistors instead of the demo circuit, and I dont have the PT-1000 connected, I just have a dummy resistor of around 1000k Ohm to check the program.

The set up we use now is this (which I have checked with direct ADC is wired correctly):

The two pins are configured as

Should this be functioning? AKA must the problem be with my wiring or accuracy of resistors etc.?

I notice there are some components on the demo board I dont have (according to datasheet related to memory functions), shown below

Do I need this to make it work?

  • 0
    •  Analog Employees 
    on Oct 19, 2020 5:11 PM 1 month ago

    Hi ,
        The components on the demo board are an EEPROM so the demo software can automatically recognize and load a config for a specific demo board. It does not impact the operation of the software when you edit the config manually. 

        The config looks OK - that should work. I would double check your wiring (including the required GND on CH2 since you have specified "No Sharing" - there is no internal ground in that config), and the values of your resistors - a 1k stand-in for RTD and a 2k Rsense would work. I'm assuming it's a typo but you mention 2000k Ohms which would definitely be out of range. 

        Are you still using the DC2209A or is this a new custom board with the LTC2983 on it?

    -Logan

  • Hi LoganC

    Thanks for the quick reply. You are right the 1000k and 2000k ohm resistors were typos.

    Good point with the grounding, I have attached the ground  to CH2 (it werent connected before), but I still cant get it to work. The output message is still -999 byte and the direct measurement is floating and fluctuating

    I noticed the dummy resistor I am measuring is actually 1050 ohm, so I replaced it with one that I measured to 999-1003 ohm, but the temperature measurement still did not work. The RSense is measured to 1999 ohm.

    Since the measurement was floating I imagined it might be due to lack of proper grounding, so I clamped an external ground to my entire frame - the floating stopped for the most part, but the raw out is now around 200 000 with the Out Deg C being -999 still.

    Im starting to think I may have damaged the Linduino or the LTC2983 board.