I bought this particular meter at a Gray's auction last year, and it came with wires dangling out of the battery compartment, and what looked like a dc plug connector for a plug pack...
The meter was originally designed to use 4V Mallory TR 233R Mercury batteries, but they haven't been made for years.... probably because of the mercury issues. So I decided to replace the mercury battery with a 3.7V lithium, and after checking the standard dimensions for a SAFT 25500 lithium battery, it would be a perfect fit. But the chinese 25500 battery I bought off ebay was 3mm longer than the standard said it should be, and wouldn't fit the battery compartment.... back to square 1.
If I could get a SAFT VL25500 the problems would be over, and I'd have a working meter... no such luck.
I eventually found a lithium thionyl chloride 3.7 Tekcell that was the standard C cell dimensions, so when it arrived I removed the dangling wires and cleaned up the battery contacts.. and away it went.. The Lithium thionyl chloride battery although it's the right size, it's not rechargeable, they are mostly used for memory backup systems and very low current applications.
The standard C cell, vs the Chinese C Cell :)
The TekCell C cell size is a whopping 8500 mAh capacity, so I thought I'd measure the power consumption, and see how long the battery will last.
The meter drew, 3.4 mA when on, and still drew 2 mA when the front panel switch was off... strange.. time to look inside.
Some idiot had wired up a TO92 3 terminal regulator with some 10 turn trim pots, no doubt to regulate the voltage from the plug pack they were using..
Well at least they protected the meter from overvoltage damage..
After removing all the extras and re-wiring it as per original, the power consumption dropped back to a comfortable 1.7 mA and zero when switched off.
So calculating the battery life, that's 8500 mAh / 1.7 that's about 200 days at 24 hours per day, If I remember to switch it off each time, it should last a few years.
One of the nice feature of electronic indicators, when compared to the mechanical indicators is the long sensing range and selectable sensitivity,
Ray
The meter was originally designed to use 4V Mallory TR 233R Mercury batteries, but they haven't been made for years.... probably because of the mercury issues. So I decided to replace the mercury battery with a 3.7V lithium, and after checking the standard dimensions for a SAFT 25500 lithium battery, it would be a perfect fit. But the chinese 25500 battery I bought off ebay was 3mm longer than the standard said it should be, and wouldn't fit the battery compartment.... back to square 1.
If I could get a SAFT VL25500 the problems would be over, and I'd have a working meter... no such luck.
I eventually found a lithium thionyl chloride 3.7 Tekcell that was the standard C cell dimensions, so when it arrived I removed the dangling wires and cleaned up the battery contacts.. and away it went.. The Lithium thionyl chloride battery although it's the right size, it's not rechargeable, they are mostly used for memory backup systems and very low current applications.
The standard C cell, vs the Chinese C Cell :)
The TekCell C cell size is a whopping 8500 mAh capacity, so I thought I'd measure the power consumption, and see how long the battery will last.
The meter drew, 3.4 mA when on, and still drew 2 mA when the front panel switch was off... strange.. time to look inside.
Some idiot had wired up a TO92 3 terminal regulator with some 10 turn trim pots, no doubt to regulate the voltage from the plug pack they were using..
Well at least they protected the meter from overvoltage damage..
After removing all the extras and re-wiring it as per original, the power consumption dropped back to a comfortable 1.7 mA and zero when switched off.
So calculating the battery life, that's 8500 mAh / 1.7 that's about 200 days at 24 hours per day, If I remember to switch it off each time, it should last a few years.
One of the nice feature of electronic indicators, when compared to the mechanical indicators is the long sensing range and selectable sensitivity,
Ray
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