Checking of Instrument Loop Continuity

Simple. The transmitter is either working or it isn't. If it isn't, try reversing the connections at its outlet terminals first.

You might also need to simulate the transmitter at different levels of 4..20 mA signals (say 0%, 25%, 50%, 75% & 100%) and confirm that this signal is indicated in the DCS or HOST system at correct Tag. By doing so, you make sure that Transmitter is correctly connected at correct Input address.

Regards,

If you are doing this frequently, it might behoove you to invest in one of these.

If this is a new installation then a proper loopcheck should be done by simulating from the transmitter end and checking the responses/operation of every other entity which is part of the loop i.e. the input device (transmitter, switch, sensor etc.), monitoring and control system (DCS, PLC etc with all operator interface and logic functions such as controller actions, alarm settings and annunciation etc.) and output devices (valves, lamps, horns, motors etc.).

If by "continuity" you mean the integrity of electrical connection i.e. cables, terminations etc, then simple continuity testing and/or insulation resistance testing (meggering) may be required. This would usually be done if an existing installation is suspect (no power to field instrument, intermittent signal at DCS or PLC etc.), and also for a new installation as part of the QA/QC programme in order to ensure the integrity of the equipment being installed.

I hope that this helps.