
Operating Instructions Chapter 3
3-1
3.1 Introduction
The Model 5182 has been designed to be extremely easy to setup and use. It can be
powered from an external source or from internal alkaline cells as selected from a
front-panel switch. In operation, the signal to be measured is to the input BNC
connector. The output is cabled directly to the input of the lock-in amplifier or other
instrument with which the 5182 is to be used.
3.1.01 Power Switch
The three-position power switch allows EXTERNAL, OFF, or BATTERY to be
selected. To operate the Model 5182 from an external power source, set the switch to
the up position. To operate the 5182 from internal batteries, set the switch to the down
position. In the center position, the 5182 is unpowered. The status of the selected
power source can be ascertained at a glance by pressing the POWER TEST button;
the adjacent LED will light if the power source voltage, whether the external supply or
internal batteries, is above the minimum required value for reliable operation.
3.1.02 Inputs
The 5182 INPUT connector is at virtual ground. It is DC coupled and is capable of
sinking considerably more DC current than the AC current which it is measuring. The
current source should be connected to the input by means of a low noise coaxial cable
and BNC connector. Since cable capacitance can cause frequency response peaking,
the cable length should be kept as short as possible, particularly on the more sensitive
ranges.
3.1.03 Sensitivity Switch
The five position sensitivity switch provides a trade-off facility between sensitivity,
noise, bandwidth and DC overload capability. AC sensitivity is switchable in decade
steps from 10-5A/V to 10-8A/V with an additional low noise 10-8A/V setting. The
corresponding DC sensitivity ranges from 10-3A/V to 10-8A/V.
3.1.04 Outputs
Two BNC output connectors are provided; one representing the AC signal current and
one representing the DC signal current. The AC Output can deliver >10 V pk-pk into
loads >100 kΩ. The 450 Ωoutput impedance provides a convenient 10:1 output
attenuator if the amplifier is loaded with 50 Ω, which can be useful if the 5182 is
required to drive coaxial cable lengths of greater than one meter at signal frequencies
approaching 1 MHz. The DC output provides a useful bias current monitor in several
applications. It can output > ±9 V from an output resistance of 10 kΩinto loads
>1 MΩ