DC NANOVOLT AMPLIFIER A14

The EM DC Nanovolt Amplifier model A14 is a very low level, very high linearity, precision measuring instrument in the EM range and represents years of research and development in the field of accurate low level measurements.
The A14 is ideal for use where very small D.C. potentials need to be measured with a high degree of accuracy. A 100 microvolt signal may be amplified and then measured to an accuracy of one part per million, the input resolution of 100 picovolts being raised to an output resolution of a much more manageable one microvolt.
The dynamic range of the A14 is very wide, for example, on the X100 range, the maximum input is 20 millivolts, while the resolution is limited by the instrument noise, which is the equivalent of a perfect 5 ohm resistor.
There are two inputs. 'Input 1' is the low noise input, with the amplifier gain switched in decades from one hundred to one million.
There is a second amplifier, with a gain of 10, connected to 'Input 2', which is used when signals greater than 20mV need to be amplified. There are two outputs, one direct and the other isolated.
The full linearity specification applies to the direct output, although the isolator also has a fairly high degree of linearity. There is a four and a half decade digital liquid crystal display, and also an analogue meter, with a centre zero mirror scale. The sensitivity of the analogue meter is increased by a switched gain extra amplifier, giving it a maximum sensitivity of plus and minus 20 nanovolts, thus allowing the A14 to be used as a sensitive null detector as well.
A filter switch on the front panel gives 3 different low pass responses and an 'off' position, in which the amplifier output is taken to the rear panel direct output, bypassing the filter amplifier. The low level input terminals at 'Input 1' are pure copper, designed to give very low thermal emf and to make connecting to the A14 easy. A plug-on terminal shield is provided.
The instrument is battery operated, with an integral charger, and so may be used in a 'floating' configuration, without adding to interference and common mode problems.

SPECIFICATION DC NANOVOLT AMPLIFIER MODEL A14

Click here for graphs : Noise and Impedance Characteristics

Input 1
Gain 5 ranges. X100, X1K, X10K, X100K, X1M.

Noise
Equivalent noise resistance 5 ohms. Peak to peak noise voltage depends on filter setting. Filter 3 gives peak to peak noise voltage of 250 picovolts with short circuit input.

Resolution
100 picovolts.

Zero Drift
Better than 300 picovolts per degree C.

Linearity
Direct Output. 1 ppm. Isolator. 100 ppm.

Source Resistance Range
0 ohm to 100 K ohm.

Input Impedance
Greater than 1 M ohm, 3 seconds after a step input, increasing with time to greater than 10 G ohm.

Offset Current
May be reduced to zero by the control at the front panel. Temperature coefficient better than 10pA per degree C.

Input 2
Gain. X10. Equivalent noise resistance 100 K ohm. Zero Drift. Typically 50nV per degree C. Input Impedance. Greater than 10 M ohm. Offset Current. Better than 10pA per degree C.

Meter Gain
X1, X10, X100. Switched at the front panel.

Accuracy
Direct Output. +/-0.02%. Isolator. +/- 0.5%. Digital Meter. +/-0.02%.              Analogue Meter 2%.

Filter
3 Position low pass plus a '0' position, which bypasses the filter.
Response Times 0. 22 milliseconds  1. 220 milliseconds. 2. 1 second. 3. 5 seconds.

Series Mode rejection
Greater than 80dB at 50Hz

Outputs
Direct. +/- 2V fsd Isolated +/- 2V fsd.

Output Resistance
Filter 0. 1K ohm. Filter 1, 2 or 3. 50 ohm. Isolated Output. 50 ohms.

Isolation
Input to case or output. Greater than 100G ohm.

Meters
Digital. Four and a half digit LCD display.                                                       Analogue. 80mm mirror scale, centre zero, calibrated 2-0-2.

Connectors
Input 1. Low thermal emf pure copper terminals. Input 2 and Case. 4mm terminals. Terminal shield provided. Outputs. 4mm sockets at rear.

Power Supply
Internal chargeable batteries, giving more than 50 hours operation from a full charge. Mains powered charger fully charges the batteries in 16 hours with the instrument switched off or 20 hours when in use. Power required 240V or 110V. 50Hz or 60Hz. 5VA. There is an alternative input to charge the batteries from an external, low noise, current source. Minimum voltage. 20V. Battery capacity. 1.2AH. NB. External charger must be a current source.    

Dimensions
314mm (12.4”) Wide. 322mm (12.7”) Deep. 179mm (72) High, including folded feet.

Weight
12Kg (26.5 lb.)