The human ear is highly perceptive, and after listening for a short time to HART communications, it can distinguish between a healthy network and one that has problems. Listen to the following communications of a host periodically polling a field device.
HART Communication Example 1 The communication is compliant and you can hear both the host and the field device. Sometimes the field device answers very quickly and sometimes you can hear a very brief silence between the request and the response. Also, there is a short silence between the request/response cycles. This silence allows for another host to get on the bus. In the next audio you can also hear a host periodically talking to a field device. In addition, several times you can hear a handheld also on the bus. It is has a slightly different tone (it is actually a little louder).
HART Communication Example 2 Using the HART Signal Detector, listen to your "good" loops and the a loop that is having problems. You will hear the differences. For example, a bad loop may have a loud hum from interference or noise bursts (static) that shouts over the HART communication. You can even listen to a loop during commissioning for noise and static before attempting communication between the host and field device. The HART Signal Detector is a low cost, high value tool that helps you understand your HART loops. A great addition to your tool bag. Fun Fact: The headline for this snippet was inspired by this song by Tom Petty and the Heartbreakers
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