EM Electronics.


This new magnetically coupled electronic isolator is designed to be used with EM DC Nanovolt Amplifiers.

One problem with very low level DC measurements is that they are prone to interference from noisy power supplies and also from the device that they are coupled into.

The power supply problem can be overcome by using batteries and this reduces the problem of interference from noisy power supplies, but this still leaves the problem of noise from the device which follows the amplifier. This is a more difficult problem to overcome and nearly always requires a very high gain to be used in the input amplifier.

One other very important advantage of having an isolated supply and also isolating the output of the DC preamplifier is that the amplifier can be used in differential mode. This is very important for many measurement applications, and allows the amplifier to measure small signals with a high degree of common mode voltage present.

These isolators may be used with the EM Nanovolt Amplifiers and this makes measurements much easier without the recurrent problem of interference limiting the level of possible resolution.

The I73 is magnetically coupled and provides a high degree of isolation, making ultra-low level DC measurements much easier.

The I73 provides for a linear isolated reproduction of the DC output of small amplifiers and can be used with the A22, A23, A39 and also with the larger amplifiers, the A10, A20 and A30 amplifier modules in the EM range.

The power necessary to operate the amplifier modules is provided with the same degree of isolation achieved for the signal.

The isolated signal noise specification is better than 1 microvolt peak to peak, which, if a gain of 10000 is used for the Nanovolt Amplifier, will add just 100pV, referred to the input of the amplifier.

The isolation resistance is much greater than 100G ohms, in dry air, thus rendering the I73 along with a suitable Nanovolt Amplifier ideal for many measurement applications.

The accuracy of the DC signal is also very good, being better than 0.5%, with a linearity specification of 0.1%

There are 2 outputs, the first is a direct output which gives a rise time constant of 100 milliseconds and there is also an active filter output which has a rise time constant of 1 second.

The input power supply required is plus or minus 8 volts to 12 volts at 10 milliamps and the isolated power output provides plus and minus 6 volts at 3 milliamps.

The I73 is housed in a very high isolation resistance enclosure, ensuring that the common mode resistance is extremely high connection, making low level isolated DC measurements convenient and easy.



Plus or Minus 3V DC





Isolated Output, Direct. +/- 0.5%

Isolated Output Filtered +/- 0.5%


Output better than 0.1%


Zero Drift
Output: Better than 1uV per degree c.


1 micro-volt peak to peak with a rise time constant of 100 milliseconds.


Input Impedance
Greater than 100 Mohm


Input Offset Voltage

Better than 25uV.

Typically 6uV


Input Voltage Offset Temperature Coefficient  

Better than 100nV per deg C

Typically 50nV per deg C


Offset Current
Less than 1.4 nA.

Typically 160 pA


Response Time Constant

Isolated Direct Output: 100 milliseconds

Isolated Filtered Output: 1 second

Direct output with a rise time constant of 100 milli-seconds.

4 pole active filtered output with a rise time constant of 1 second.


Resistance: Common Mode >> 100G ohms.


Common Mode Rejection Ratio

Greater than 160dB DC


Isolated Connections.

Inputs. 3mm solder tags for signal input.

Outputs: 3mm solder tags for plus and minus output power and isolated 0v.


Non Isolated Connections:

Power Input: 3mm solder tags for plus and minus supply voltage and 0v.

Signal Outputs: 3mm solder tags for direct and filtered outputs.


Power Supply Requirement
Plus and Minus 8 volts to 10 volts. 10 milliamps


Output Power

Plus and Minus 6 volts

5 milli-amps with A10 connected


Length: 135mm (5.3)
Width: 82.5mm (3.25")
Height: 53mm (2.1") Including terminals.


115g (4oz)




About EM Electronics

Selecting the Correct Nanovolt Amplifier


Low Level Voltage Measuring Instruments


Ultra Low Level DC Voltage Amplifiers

Low Level DC Voltage Amplifier Modules

PC Boards for Modules 


Contact EM Electronics

Summary information regarding our products is already included within this Website, we are adding further product specifications details.

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