Adjustment Of The Monitor's 4 To 20 Ma Current Loop Interface - GE Bently Nevada 1900/27 Operation And Maintenance Manual

1900/27 Vibration Monitor Operation and Maintenance Manual
The zero point of the LCD is now properly set. There is no span adjustment for the
LCD display. This zero adjust procedure zeros the LCD display for the monitor only.
Once a transducer is connected to the monitor, a low value LCD reading, less than
0.250 mm/s (0.010 in/s), will be present when no vibration is present. This reading
results from the electrical noise floor of the transducer and monitor system.

4.2.2 Adjustment of the Monitor's 4 to 20 mA Current Loop Interface

Use this procedure to adjust both the zero and the gain of the analog signal from
the monitor's 4 to 20 mA output to the plant computer. These adjustments should
be done by a skilled electronics technician or engineer at an electronics
workbench rather than at the installation site. The procedure to adjust this
interface requires the following tools and equipment:
• A small straight blade screwdriver.
• A power source for the monitor being calibrated (110 Vac, 220 Vac, or +24
Vdc).
• A 3-conductor cable for attaching the power source to the monitor.
• A power source for the 4 to 20 mA interface (+14 Vdc to +30 Vdc, see
Appendix A for complete specifications).
• A 2-conductor cable for attaching the power source to the 4 to 20 mA
interface.
• A calibrated multimeter with floating inputs.
• A calibrated sinewave generator that can generate-a floating 1.3 V
sinewave at 614 Hz.. (The output must be floating. Neither one of the two
terminals of the sinewave output can be grounded.)
• Four 3 k resistors.
• Several 50 mm (2 inch), 18 AWG wires.
32
ms