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For example, in an analog lock-in, the PSD input range might be 5 V. With 60 dB dynamic reserves, the signal will be
only 5 mV at the PSD input. The PSD typically has no gain so the DC output from the PSD will only be a few millivolts.
Even if the PSD had no DC output errors, amplifying this millivolt signal up to 10 V is error prone. An offset as small as 1
mV will appear as 1 V at the output. This is one of the reasons why analog lock-in does not perform well at high dynamic
reserve.
The digital lock-in does not have an analog DC amplifier, and has no DC output offset. Likewise, the digital DC amplifier
has no input offset. The output of the digital DC amplifier is simply the product of the input signal and the required gain.
This allows the SE1022D to operate with 100 dB of dynamic reserve without any outputs offset or zero drift.
1.6 DC Outputs and Scaling
The SE1022D has Channel 1 and Channel 2 outputs (CH1 and CH2) on the rear panel.
CH1 and CH2 Outputs and Display
The output voltage range of CH1 and CH2 is from -10V to 10V.
The output signal is proportional to the value of the test signal and the setting scale.
Fig.6 Channel Output Display Interface of SE1022D
The unit and position of decimal point of data displayed on screen can be adjusted manually, or automatically through
‘AutoSet’ buttons which is very convenient to adjust the accuracy.
X, Y and R Output Offset and Expand
The SE1022D has the ability to offset the X, Y and R outputs, which is useful when measuring deviations in the signal
around some nominal value. The output can be offset to zero by setting the offset. Then changes in the output can be read
directly from the display or output voltages. The offset is specified as a percentage of full scale. Offsets can be set up to
100% of full scale. When the sensitivity is changed, the percentage does not change.
The X, Y and R outputs of both channels A and B can be expanded. It's realized by multiplying the output with an
