Drive Voltage - Protek 9216A User Manual

Drive Voltage

The 9216A meter has three fixed output rms voltages, 0.1 V, 0.25 V and 1.0 V.
These voltages are selectable from the front panel. A variable rms voltage is also
available, which is adjustable from 0.1 V to 1.0 V with 50 mV resolution. The
accuracy of the voltage levels is 2% or greater. To select a fixed voltage, press
and release the VOLT key located in the DRIVE VOLT section on front panel
keypad until the LED indicates the desired voltage.
To set the variable output voltage:
1. Press the CAL keypad button. The DISP LED will indicate the ENTRY
mode. On the alphanumeric display, "vtest" and the current voltage will be
shown.
2. Enter the desired output voltage from the numeric keypad (0.1 to 0.9 may
be entered) and press ENTER (M H µF key).
3. The output voltage may be set in 50mV steps. NOTE: If the drive voltage
is a value other than one of the three fixed voltages the CONS LED will light .
The output voltage is applied to the device under test through a source
impedance. Thus, the voltage across the device is always less than or equal to
the output drive voltage. The available source impedances for the four auto
ranging selections made by the meter are 25  (Range 3), 400  (Range2), 6.4
k (Range 1) and 100 k (Range 0), all of which are accurate to 2%. The
source impedance is automatically selected as a function of the measurement
range, unless the unit is in the constant voltage mode. In the constant voltage
mode, the source impedance is always 25 . See the section on Range for
determining which measurement range the meter is using.
Figure 3-1 shows the voltage across the Device Under Test (DUT) vs. the
DUT impedance for the different measurement ranges.
normalized to a 1.0-V output drive setting for different applied voltages; that is, the
Figure plots the normalized voltage across the DUT, given by
(V
Note that the voltage applied to the DUT is nearly equal to the output voltage at
the upper end of each range and decreases due to lower impedance toward the
lower end of the range. This is because of the impedance of the voltage source.
If the meter is in the constant voltage (CV) mode, the source impedance is always
set to 25 . For any DUT with impedance significantly larger than 25, the
voltage across the part is essentially equal to the output drive voltage.
For most devices, including resistors and capacitors, and for many inductors,
the 1.0 Vrms setting is the most appropriate setting. For some inductors and for
semiconductor or active devices, such as diodes and transistors, the 0.25 or 0.1
Vrms setting should be used. Certain devices require a specific test voltage, such
as Z5U ceramic disk capacitors (test voltage = 0.5 Vrms). In these cases, use a
variable voltage setting to obtain the exact voltage required. In general, use the
largest voltage possible for the best signal-to-noise ratio and accuracy.
/V ) = R /(R
DUT source DUT source
21
The values are
+ R )
DUT