What is an electrometer?
Like the digital multimeter (DMM), the gersley electrometer is an instrument used to measure charge, current, voltage and resistance. However, the electrometer has a charge measurement resolution of 10fc, a current resolution of 100aa, and an impedance measurement capability up to 200t Ω, which surpasses the standard digital multimeter. Electrometers are used in situations where extreme sensitivity or various types of sensitive electronic circuits are required.
Simplified measurement of high resistance of materials by using geothley electrometer
High resistance measurement
The most common measurement method of resistance is digital multimeter, which has a measurement range of about 200m Ω. However, in some cases, it is necessary to accurately measure the resistance in gigaohm and higher ranges. These include applications such as characterizing high megohm and gigaohm resistance, determining the resistivity of insulators, and measuring the insulation resistance of printed circuit boards. These measurements can be made with the help of an electrometer, which can simultaneously measure very low current and high impedance voltage.
Common high resistance measurement
Insulation resistance: the insulation resistance is the ratio of the DC voltage applied between the two electrodes to the total current between the electrodes. Examples of insulation resistance measurement include measuring leakage current between wires on a printed circuit board, or resistance between conductors of a multicore cable.
Volume resistivity measurement: volume resistivity refers to the resistance of insulating material passing through 1cm3, expressed as ohm cm, Ω· cm).
■ surface resistivity measurement: the surface resistivity is the resistance between two electrodes on the surface of insulating material, and expressed in ohm (usually for clarity, the unit is ohm per square, that is, Ω · □).
Features of jishili electrometer:
Operation similar to DMM
The 6514 and 6517b electrometers feature easy DMM like operation through the front panel, with a single button controlling important functions, such as resistance measurement. They can also be controlled through a built-in IEEE-488 interface, which enables people to program all functions through the bus with the help of a computer controller.
However, unlike digital multimeter, electrometer has lower bias current and input burden. The input bias current of model 6514 or 6517b is less than 3fa. Usually, the bias current of a digital multimeter is tens or hundreds of picoamps. In contrast, this severely limits their ability of weak current measurement.
Scan card (6517b)
Two kinds of scan cards can be provided to simplify the scanning of multi-channel signals, such as the test in the production of capacitors or other circuits. Each scan card can be easily inserted into an optional slot on the back panel of the instrument. The 6521 scanning card can provide 10 channels of weak current scanning. The 6522 scan card provides 10 channels with high impedance voltage switching or weak current switching capability.
Measuring resistance / resistivity by alternating polarity method (6517b)
The model 6517b uses the alternating polarity method to measure the impedance / resistivity, which almost eliminates the influence of any background current in the sample. The first and second order drift of the background current is also eliminated. Alternating the polarity of the applied voltage usually results in a highly repeatable and accurate resistance (or resistivity) measurement.
Editor in charge: GT