Martel Electronics 135 - Manual (Page 50)

Loop Power Supply (Optional)
The Loop Power Supply (LPS) is an option that provides 24 VDC to
power a device under test. The LPS is shipped with the batteries in an
uncharged state.
The battery charger for the LPS is different from the one supplied with
the Model 130/135 and 230/235 calibrators.
The LPS contains eight (8) AA Ni-Cd batteries that provide power to a
DC to DC converter. This converter boosts the battery voltage (10.6 to
9.2 volts) to 24 VDC +/- 5%. The LPS is intended for use as a power
supply for any two wire, 4 to 20 milliamp instrument requiring 24 VDC
power. Battery life is 6 hours nominal at 20 milliamps. Full
specifications can be found on page 71.
The LPS is designed to turn itself ON and OFF automatically, based on
current demand. When a series loop exists at the LPS Loop Power jacks
calling for .5 milliamps or greater the LPS will automatically turn ON.
Open the loop and power down occurs. This allows for maximum
battery life by not allowing the unit to be left in the ON mode
accidentally.
The LPS can be used with or without the calibrator. When the test
leads are connected from the LPS Loop Power connections to a device
requiring power, the LPS automatically turns itself ON and provides
24VDC. Breaking the connections causes the LPS to automatically turn
itself OFF, preventing needless battery drain.
To use the calibrator with the LPS, simply plug the special connector
provided with the LPS from the plug marked “To mA Input” on the LPS
to the milliamp input terminals on the calibrator. This automatically
Output Functions
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Note: Before using the LPS as a portable unit, it is necessary to
charge the batteries for a minimum of 14 to 16 hours.