Q: Is the SPA2 Limit Alarm Trip compatible with HART and able to pass HART through the unit? Our application is a control valve with a loss of signal cut out. We are using the SPA2 for this with position feedback via a Tri-Loop.
A: The SPA2 HLPRG model can be added to an existing HART loop without disrupting the existing HART communications on the loop. However, the optional analog output of the SPA2 will not contain any of the HART digital components so it won’t be useful for connecting to the Tri-Loop.
Our HIM HART Interface Module has the same functions as the Tri-Loop along with optional alarm relay outputs, transmitter power supply, and a display. You may be able to use this in place of both the SPA2 and the Tri-Loop. The HIM only monitors the HART digital signal and not the 4-20mA, so you may need to address the loss of signal differently. Use a suitable HART diagnostic or status bit such as “device malfunction” or “output current fixed” to drive one of the HIM’s relays outputs.
If you just need a signal isolator to pass the HART signal we have several isolators that can do this:
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