Output Check Procedures; Constant Current Source Mode Procedure; Figure 15 - Current Loop Test Connections - Honeywell ST 700 User Manual

3.7.3 Output Check Procedures

The Output Check comprises the following procedures:
•
The Loop Test procedure checks for continuity and the condition of components in the output
current loop.
•
The Trim DAC Current procedure calibrates the output of the Digital-to-Analog converter for
minimum (0%) and maximum (100%) values of 4 mA and 20 mA, respectively. This
procedure is used for Transmitters operating online in analog mode to ensure proper
operation with associated circuit components (for example, wiring, power supply,..., control
equipment). Precision test equipment (an ammeter or a voltmeter in parallel with precision
resistor) is required for the Trim DAC Current procedure.
•
The Apply Values procedure uses actual Process Variable (PV) input levels for calibrating
the range of a Transmitter. To measure a liquid level for example, a sight-glass can be used to
determine the minimum (0%) and maximum (100%) level in a vessel. The PV is carefully
adjusted to stable minimum and maximum levels, and the Lower Range Limit Value (LRV)
and Upper Range Limit Value (URV) are then set by commands from the MC Toolkit.
The Transmitter does not measure the given PV input or update the PV output while
it operates in the Output mode.

3.7.4 Constant Current Source Mode Procedure

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Figure 15 – Current Loop Test Connections
ST 700 SmartLine Pressure Transmitters User's Manual Revision 1.0