Facing problem in 0 to 5 v furnace control

[Franklin Eden]

Hello there

I'm facing problem with furnace hating control.
The 0 to 5 volts control voltage is supplied by DaC1220E . As soon as I turn on the instrument the DAC supplies 2.4 Volts instead of 0 Volt . The input to the DAC is from 20 bit pic controller and 2.5 v reference voltage .
I replaced the DAC still the problem persists . The 5 V digital supply is good.

Looking forward for your suggestions to fix this

 

[Alec_t]

Welcome to EP!

I replaced the DAC still the problem persists . The 5 V digital supply is good.

Then probably there's a software bug or a wiring error.
Can you post your schematic?

 

[Harald Kapp]

If you perform caibration as suggested on page 13 of the datasheet your observation could be the rsult of a featire of the DAC.
The datasheet states on page 6: "the output changes during calibration.." and "Offset calibration is performed by setting the DAC output voltage to mid-scale..." The observed 2.4 V is approx.mid scale, so it coul be the result of calibration.
The datasheet also states on page 6. "The output changes during calibration, but can optionally be disconnected during the procedure.". Going this way may solve the issue.

 

[Franklin Eden]

Welcome to EP!

Then probably there's a software bug or a wiring error.
Can you post your schematic?

This is the schematic showing A PIC controller and the DAC . The DAC gets the input from PIC