Percent
Percent selects the percentage calculation and lets you specify a reference value. The
displayed reading will be expressed as a percent deviation from the reference value. The
percentage calculation is performed as follows:
where: Input is the normal display reading.
Reference is the user entered constant.
Percent is the displayed result.
Configuration
To configure the percent calculation, perform the following steps:
1. Press SHIFT then % to display the present value:
REF:+1.000000^
2. Enter a reference sign, value, and units prefix. Use the and keys to choose a
numerical place and use the ▲ and ▼ keys to increment or decrement the digits.
3. Press ENTER when done.
The Model 2010 will display the result of the calculation. The result is positive when the input
exceeds the reference and negative when the input is less than the reference. Engineering units
are used to show values in the range 1 nano to 1000G. Exponential notation is used above that
range.
dBm calculation
dBm is defined as decibels above or below a 1mW reference. With a user-programmable
reference impedance, the Model 2010 reads 0dBm when the voltage needed to dissipate 1mW
through the reference impedance is applied. The relationship between dBm, a reference
impedance, and the voltage is defined by the following equation:
Where: V
IN
is the DC or AC input signal.
Z
REF
is the specified reference impedance.
NOTE Do not confuse reference impedance with input impedance. The input impedance of
the instrument is not modified by the dBm parameter.
If a relative value is in effect when dBm is selected, the value is converted to dBm, and then
REL is applied to dBm. If REL is applied after dBm has been selected, dBm math has REL
applied to it.
Percent
Input - Reference
Input
------------------------------------------
100%×=
dBm = 10 log
V
2
IN
/Z
REF
1mW
---------------------------------
2-34 Basic Measurements
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