Input
The charge that is to be measured is applied to the input socket IN via a
conductor ball.
The COM socket is connected to the grounding (protective conductor,
water pipe, … )
An internal 10nF capacitor is positioned between the input sockets.
Output
The output voltage of the device follows the voltage of the internal capacitor
up to the measuring range limit.
Due to an internal 1kΩ resistor the output voltage is converted into a
current (3V → 3mA) and at the same time the output is protected against
short circuit.
Operation
The device is switched on with the toggle switch in the middle.
By pressing the reset button the capacitor gets discharged.
The Electrometer is equipped with an integrated 9V battery but can also be
operated by any plug-in power supply with an output voltage of 6 - 12V DC.
The battery should be removed from the device if it is not expected to be
used for a long period of time. Damage to the device due to leaked
batteries is not covered by the guarantee!
The service life of a standard alkaline transistor battery is around 38 hours
of operation.
As long as the green LED glows the Electrometer is turned on and thus
the battery or the power supply are properly working.
If the LED glows red than the supplied voltage is too low and the
Electrometer does not work anymore.
If the supply voltage exceeds 15V the device is switched off; if the supply
voltage exceeds 25V the device can be destroyed.
Reverse polarity supply voltages are problem-free up to 25V.
Notes on experimental practice
It is essential to ground the COM socket!
Due to the high sensitivity of the device, the user is tempted to
leave the grounding of the COM connection to various parasitic
capacitances. Especially after a few attempts, this leads to the
experimental setup itself being charged. The result is poorly
functioning attempts and unpleasant discharges on the part of the
user against furnishings.
Ground test subject, take off your shoes and
work calmly and quietly!
Attention should also be paid to the self-charging of the user,
otherwise tests will work asymmetrically (e.g. only positive
charges, negative ones not) and unpleasant discharges against
furniture can occur, especially after longer test series.
Only work with dry utensils, wear gloves if necessary.
Remove dirt films with gentle non-ionic
grease solvents (e.g. mineral spirits).
If charging attempts do not work, the reason behind it is often too
high humidity. Especially experiments with acrylic glass rods as
well as paper or textiles become more difficult when the hands are
wet or the humidity is high.
Beware of electrically conductive cleaning and impregnating
agents! Glass and acrylic glass are sometimes coated with an
anti-static coating. Logically, this is counterproductive!
