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Electroscope Circuit to Measure Electrostatic Charge

One tool for checking static electricity is Electroscope Circuit to Measure Electrostatic Charge.

Static electricity happen when object have unbalanced electric charges.

Electroscope help to know if static electricity is there and it is how much.

It just simple conductor.

When something touches it then electroscope charge changes and react.

This movement show what charge was before.

Circuit Working:

Parts List:

CategoryDescriptionQuantity
Resistors
100k 1/4 watt2
10k 1/4 watt1
R4 (2 to 20k range)1
Capacitors
Ceramic C1 (1 to 2μF range)1
Electrolytic 1μF 16V1
Semiconductors
IC MAX 43222
ON/OFF Switch1
Meter 100uA center 01

This DIY electroscope circuit help to find electrostatic charge properly.

Capacitor C1 is good MKT capacitor and its value is from 1 to 2μF which keep the charge we want to measure.

Formula is U = Q / C1.

It tell how voltage U and charge Q are related in capacitor C1.

This high resistance part is safe because operational amplifier IC2 protect it.

One side of capacitor C1 connect to input wire with test probe.

Other side goes to ground wire this is ground point.

IC2 gives power to meter M1 (±100 μA to ±1 mA center zero) it make low voltage from IC1 stronger.

Switch S1 give two choices for measuring.

When S1 open the gain is 5 and when S1 is closed then gain become 10.

Meter M1 has inside resistance 2.2k ohm.

Resistor R4 from 2 to 20k is not needed if used digital multimeter instead of M1.

This circuit uses MAX 4322 operational amplifiers from Maxim.

These op-amps can work from one rail to other and output can go to power level with normal input voltage.

Formula:

MAX 4322 is good low-noise op-amp made by Maxim Integrated.

It is used for many works where high accuracy and low noise is needed.

Many people use MAX 4322 in amplifier circuits where noise must be low like voltage follower.

To make MAX 4322 detect electrostatic charge we connect it as high impedance buffer to the electroscope sensitive parts.

When using MAX 4322 for measuring electrostatic charge we must remember this is just a simple formula:

Av = Voltage Gain

MAX 4322 can work as unity gain amplifier or voltage follower.

In this setup voltage gain Av is around 1.

Input and Output Resistance:

MAX 4322 is good for high impedance sensors or electrodes because input impedance is very high which is in hundreds of megaohms.

Output impedance is low so we can connect to other stages easily with no problem from loading.

Power Supply Voltage:

Be sure MAX 4322 gets correct power from VCC which is often ±15V but depends on what we do.

Noise Point:

In electroscope circuit where we measure small electrostatic charge or weak signals MAX 4322s low noise is very important.

Formula for voltage follower mode:

Input voltage (Vin) is almost same as output voltage Vout.

Av gain is close to 1.

Important Note:

When used as high impedance buffer MAX 4322 can follow and boost electrostatic charge signals from electroscope sensor.

Because of high input impedance and low noise it work very well for this.

How to Build:

To build a Electroscope Circuit to Measure Electrostatic Charge following steps are required to follow:

Prepare Components:

Connect IC1 and Capacitor C1:

Operational Amplifier IC1:

Digital Multimeter:

Switch S1 with Range of Measurements:

Verify Connections Again:

Testing:

Modifications:

Adjusting:

Complete the Circuit:

Conclusion:

This Electroscope Circuit to Measure Electrostatic Charge helps in study of physics and electronics to measure electrostatic charge.

But remember design may change in different circuits.

References:

An electronic electroscope

Electrostatic fieldmeter

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