Hi all. This is my first post here. In my position I have to design and build most (all) of my test equipment but my electronic knowledge is poor except for simple circuitry, some data acquisition, etc. I am attempting to build a PID temperature controller that is software based (Labview) and operates the oven through a basic load switch (circuit diag attached). I'm using a standard OAC5 s.s. output module to turn a logic signal into a usable power switch, driving a higher load s.s. power relay. I have chosen an AC output module & AC coil power relay because of no need for a power supply. When I energize this circuit I have power coming from the output receptacle, regardless of input or no input to the OAC5. Is there a peculiarity of these relays (in particular the OAC5) that it does not operate without a resistive load across the output? I do not have access to the circuit right now but I have breadboarded just the OAC5 to light an incandescent lamp and it works OK. It just will not go to low output when wired to the coil of the power relay exclusively. Am I correctly diagnosing the problem? If so could I switch the high side of the indicator lamp (incandescent) from terminal 2 to terminal 3 of the power relay and supply enough resistive load to force the output module to behave?
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