Download RF Lock-In Amplifier - Frederick Seitz Materials Research Laboratory

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10
Outputs, Offsets and Expands
Press CH1 Output to select DISPLAY.
This key toggles the CH1 analog output function
between the selected display quantity and X. In
other words, it is possible to have a signal
proportional to X on the analog output while the
display shows R (or some other quantity).
In this case, with the display set to X, X remains the
CH1 analog output quantity and the DVM reads the
same.
11
Press CH1 Display once to select R(V).
This selects R (Volts) as the CH1 display quantity.
Since the CH1 Output is set to DISPLAY, R is now
also the CH1 analog output.
Remember that Xoffset and Yoffset are applied
directly to the demodulator outputs, the value of R
is computed from the offset values of X and Y. The
XYOffs indicator in the CH1 display indicates that
the displayed value is affected by XY offsets.
At the present time, Y is offset to zero and X is
offset to 100 mV. The resultant R is 100 mV and
the CH1 display should read about 0.1 V. Expand is
off since the display quantity R has not been
expanded.
The CH1 analog output should be
(0.1 V/1.0 V - 0.0) × 1 × 10V = 1 V
or 10% of full scale.
The Channel 1 Offset and Expand keys now set the
offset and expand for R.
12
Press CH1 Output to select X.
The CH1 analog output returns to X. The offset and
expand for X are still in effect, even though R is the
displayed quantity. Thus, the DVM reads 10 V.
The CH1 display is unchanged. It still shows R and
0.1 V.
13
Press CH1 Offset On/Off.
This turns Roffset on. The ROffs indicator within
the CH1 display turns on to show that the displayed
quantity is affected by Roffset. (The XYOffs
indicator within the CH1 display means that XY
offsets are on and also affect the CH1 displayed
quantity.)
14
Press CH1 Offset Modify.
The offset of the CH1 display quantity, R(V), is
shown on the Reference display. The reading is in
percent of full scale.
SR844 RF Lock-In Amplifier