High Voltage LED on the MS4/MS16 flashes regardless of battery voltage when connected to the NC48 Rechargeable Battery

Tech Note: TN0238
Product: MS4, MS16
Version: MS4 serial numbers < 4008 and MS16 serial numbers < 4015
Date Added: 2007-09-04

Issue

When the stimulus isolator (MS4 serial numbers < 4008 and MS16 serial numbers < 4015) is connected to the NC48 Rechargeable Battery, the High Voltage LED on the front panel of the MS4/MS16 will flash constantly, regardless of battery voltage. Because the stimulus isolator was originally designed for use with the HV250 battery pack (±135 V) exclusively, the low voltage indicator is triggered even if the NC48 (±24 V) is at full charge.

MS4/MS16 devices with serial numbers > 4007 are configured at the factory for either the NC48 or HV250 according to the order specification and will indicate low voltage as expected for the configured device.

Workaround

If using an MS4/MS16 with a NC48 Rechargeable Battery, ignore the low voltage indicator and use a standard voltmeter to periodically test the voltage of the battery.