LeCroy DA1855A Operation page 5

DA1855A-OM-E Rev A
The DA1855A's amplifier subtracts the voltage applied to its
inverting input from the voltage applied to its non-inverting input.
The DA1855A output is therefore zero whenever these two
voltages are equal. For this reason, the voltage applied to the
inverting input is called a comparison voltage, V
another way, the value of the horizontal center line in the
oscilloscope graticule is the voltage read in the PVG display.
Each graticule line above or below the center line will add or
subtract the Volts/div value from the PVG setting. Refer to figure
3-1 where the horizontal center line represents a power supply
voltage of 5.030 V, the next higher line 5.050 V and the line below
the center line 5.010 V. In this figure noise on a + 5.030 V signal
is easily displayed using 5.030 Volt offset and a vertical scale
factor of 20 mV/div.
V can be used to make precise measurements of large
COMP
signals by comparing the accurately known V
unknown signal. It can also be used to measure the actual
voltage at any point of a waveform.
Since the amplifier's gain and input attenuator are individually
selectable, the comparison range can be changed from
V to 155.000 V by changing the ATTENUATION from 1 to 10,
while the overall gain can still be set either to 1 or 0.1 by selecting
either or X1 GAIN.
X10
5.050 V
5.030 V
5.010 V
Figure 3-1. Voltage Measurement
ISSUED: July 2002
Operation
. Stated
COMP
with the
COMP
15.500
3-5