Ametek 7124 Instruction Manual page 107

RATIO (2.5V fs)
When set to RATIO the corresponding DAC connector on the rear panel of the
main console outputs a voltage related to the result of the RATIO calculation,
which is defined as follows:-
 
10 X output
 
RATIO

ADC1 Input
where X output is the X channel output as a percentage of the full-scale
sensitivity and ADC 1 is the voltage (expressed in volts) applied to the ADC 1
input connector on the rear panel of the main console. Hence, for example, if the
instrument were measuring a 100 mV signal when set to the 500 mV sensitivity
setting, the X channel output were maximized and a 1 V signal were applied to
the ADC1 input, then the value of RATIO would be:-

0.1

10

0.5
 
RATIO
1.000



RATIO 2
The relationship between the voltage at the DAC connector and the RATIO
value is defined as follows:-
RATIO
+7.5
+2.5
0
-2.5
-7.5
LOG RATIO
When set to LOG RATIO the corresponding DAC connector on the rear panel of
the main console outputs a voltage related to the LOG RATIO calculation, which
is defined as follows:-



LOG RATIO log
10

where X output is the X channel output as a percentage of the full-scale
sensitivity and 1 is the voltage (expressed in volts) applied to the ADC 1 input
connector on the rear panel of the main console. Hence, for example, if the
instrument were measuring a 100 mV signal when set to the 500 mV sensitivity
setting, the X1 channel output were maximized and a 1 V signal were applied to
the ADC1 input, then the value of LOG RATIO would be:-




LOG RATIO log
10


LOG RATIO = 0.301
The relationship between the voltage at the DAC connector and the LOG RATIO
Chapter 5, FRONT PANEL OPERATION








DAC Voltage
7.5 V
2.5 V
0.0 V
-2.5 V
-7.5 V


10 X output


ADC1 input

0.1

10

0.5

1.000


5-53