FSI Customer Service Bulletin
FSI has recently discovered a potential problem with the alkaline battery pack option on the 3"Micro-CTD.
The 3" MCTD uses a charge pump circuit to "pump" the 3v battery voltage up to approximately. 7v (V+). There is another V+ regulator used on the external power input. On some MCTD's, the output of the charge-pump circuit may be too close to the output of the external supply regulator. The result of this potential condition is that the batteries will share the power requirements of the MCTD with the external supply, therefore draining the battery pack.
This potential condition occurs because of the variability of the components used. Although FSI uses only 1% resistors and quality components, the small degree of variability can have a substantial affect on the battery drain. For instance, a recent instrument in for re-calibration was seen to have a 70mA drain on the battery pack while external supply was connected. Other instruments show relatively no drain on the battery pack.
To determine if this condition exists on your 3" MCTD, simply install a current meter in series with the battery pack (or 3V power supply connected to the alkaline battery input) and measure the current drain while 12V supply is connected to external input. If there is more than a 10mA draw on the batteries, then please contact FSI for directions on repairing this condition.
If you would rather have FSI perform this correction, obtain an RMA# and FSI will gladly repair your 3" MCTD and return it to you quickly.
FSI apologizes for the inconvenience and thanks you for your patience.