28
reference
reference
Input
Percent
Where: Input is the normal display reading
Reference is the user-entered constant
Percent is the displayed result
To configure the percent calculation, perform the following steps:
1. Press
Shift
→
Rel
for percent math operation and the present reference value displays:
+1.00000
2. Use
and
keys to choose a numerical place and use
and
keys to
increment or decrement the digits. Enter a value and units prefix.
3. Press
(ENTER) to confirm the reference value. The message
―
SAVED
‖
will be displayed for a
moment.
4. TH1942 will display the result of the percent calculation.
If you want to change the parameter values when the percent math function is enabled, besides the
foregoing method you can take actions as below:
1. Press
Shift
→
to enter the menu on the menu level,
―
A: MATH MEU
‖
will be displayed.
2. Press
to move down to the command level within the MATH MEU,
―
3: PERC REF
‖
will be
displayed.
3. Press
to enter the parameter level, and the present reference value will be displayed:
+1.00000 .
4. Use
and
keys to choose a numerical place and use
and
keys to
increment or decrement the digits. Enter a value and units prefix.
5. Press
(ENTER) to confirm the reference value,
―
SAVED
‖
will be displayed for a moment, and
TH1942 will return to the command level. Press
to cancel the reference value input, TH1942
returns back to the command level without changing the reference value.
6. Press
Shift
→
key to exit the menu and return to the percent math operation status.
Model TH1942 will display measurement result of
calculation. If the value of ―Input‖ is larger than that of
―Reference‖, displayed result will be positive; contrarily, it will be negative if the value of ―Input‖ is smaller
than that of ―Reference‖.
3.9.2 dB Calculation
Expressing DC and AC voltage in dB makes it possible to compress a large range of measurements into
a much smaller scope. The relationship between dB and voltage is defined by the following equation:
REF
IN
V
V
dB
log
20
Where:
IN
V
is the DC or AC input signal.
REF
V
is the specified voltage reference level
