L4532A / L4534 AC Flatness Adjustment
This procedure adjusts the AC Flatness characteristic of the Digitizer. Two adjustments on
each channel can be made. One adjustment is done on the 4V range and the second one is
done on the 64V range.
Adjustments only needs to be done if the AC Flatness (optional test) in the service guide
exceeds it’s limits. The 4V adjustment needs to be done before the 64V adjustment, because
adjustments to the 4V also directly affect the 64V adjustment. Thus if the 4V adjustment is
done then the 64V adjustment must also be done. If only the 64V adjustment is needed then
not adjusting the 4V is OK.
The 4V AC flatness adjustment procedure consists of measuring a 2.68 Vrms, 1 kHz sinewave on the
4V range and then changing the frequency to 1 MHz and adjusting a capacitive trimmer pot until the
second measurement equals the first.
The 64V AC flatness adjustment procedure consists of measuring a 43 Vrms 1 kHz sinewave on the
64V range and then changing the frequency to 300 kHz and adjusting a capacitive trimmer pot until
the second measurement equals the first.
The test signals are generated by a calibration standard. The input signals are measured by the digitizer
using the On Board Measurement capability to calculate the RMS value of the input signals, and the
measured signal amplitudes at the two frequency points are adjusted to be equal to each other.
Equipment
Fluke 5700A Calibrator
Johanson 4192 Tuning Tool
Available from: Johanson Manufacturing Corporation, Rockaway Valley Road, Boonton N.J. 07005
(973)-334-2676
This is a small precision tool designed for the capacitive trimmer pots used in the L4532-66703 boards.
Order more than one because it can be damaged by abuse.
Adjustment Locations:
The top cover of the L4532A (two channel) or L4534A (four channel) digitizer must be
removed. The adjustment is done on the L4532-66503 board. The L4532A will have only one
board in the channel 1 & 2 position. Shown below is the L4534A that has two of the L453266503 channel boards. The capacitive trimmer pots are Agilent P/N 0121-0604 or Johanson
232-2GR1, 2.5-10 pf. C304 is the 4V trimmer and C324 is the 64V trimmer
4V Flatness Equipment Setup
1) Connect the Calibrator output to the Channel input on the digitizer. Do not connect the channels in
parallel for this test. The L4532A has two channel inputs and the L4534A has four channel inputs.
2) Make a connection to the digitizer using the web interface. See “Using the Web Interface” in the
sevice guide (L4534-90010)
3) Enter the Remote Control Page and select the Configure Digitizer tab. Set the following parameters and
click the Apply Configuration button.
All Channels:
Range ±4V
Coupling AC
Filter LP_20_MHz
Acquisition:
Sample Rate 20 kSa/s
Records 1
Samples/record 100000
Trig Holdoff 0 sec
Pre-trig Samples/record 0
Trig delay 0
Trigger:
Arm source Immediate
Trigger source Immediate
Select the Acquire Data tab.
a) Click the View Measurements... button. Delete any installed measurements.
b) Click New and select Vrms for each digitizer channel. Set the Area to Window. Set the
Coupling to AC. Click the OK button.
c) Click the Edit ... button and set the Starting Offset to 0 and Window Size to 100000. Click the
OK button.
d) Leave the Measurements window open.
4V Flatness Procedure
1) Set the Calibrator to output 2.68 Vrms at 1 kHz.
2) On the Acquire Data tab, click the Run Once button.
a) Note the Vrms measurements for the connected channel in the Installed Measurements
window.
b) Record the measured value as Vrms 1kHz.
3) Use the Configure Digitizer tab to set the Sample Rate to 20 MSa/s. Click the Apply
Configuration button.
4) Set the Calibrator output to 2.68 Vrms at 1 MHz .
5) On the Acquire Data tab, click the Run button.
a) Note the Vrms measurements for the connected channel in the Installed Measurements
window.
b) Turn Channel 4V capacitive trimmer pot until the measured value is equal to Vrms 1 kHz
64V Flatness Equipment Setup
1)Connect the Calibrator output to the Channel input on the digitizer. Do not connect the channels in
parallel for this test. The L4532A has two channel inputs and the L4534A has four channel inputs.
2) Make a connection to the digitizer using the web interface. See “Using the Web Interface” in the
sevice guide (L4534-90010)
3) Enter the Remote Control Page and select the Configure Digitizer tab. Set the following parameters and
click the Apply Configuration button.
All Channels:
Range ±64V
Coupling AC
Filter LP_20_MHz
Acquisition:
Sample Rate 20 kSa/s
Records 1
Samples/record 100000
Trig Holdoff 0 sec
Pre-trig Samples/record 0
Trig delay 0
Trigger:
Arm source Immediate
Trigger source Immediate
Select the Acquire Data tab.
a) Click the View Measurements... button. Delete any installed measurements.
b) Click New and select Vrms for each digitizer channel. Set the Area to Window. Set the
Coupling to AC. Click the OK button.
c) Click the Edit ... button and set the Starting Offset to 0 and Window Size to 100000. Click the
OK button.
d) Leave the Measurements window open.
64V Flatness Procedure
1) Set the Calibrator to output 43 Vrms at 1 kHz.
2) On the Acquire Data tab, click the Run Once button.
a) Note the Vrms measurements for the connected channel in the Installed Measurements
window.
b) Record the measured value as Vrms 1kHz.
3) Use the Configure Digitizer tab to set the Sample Rate to 20 MSa/s. Click the Apply
Configuration button.
4) Set the Calibrator output to 43 Vrms at 300 kHz .
5) On the Acquire Data tab, click the Run button.
a) Note the Vrms measurements for the connected channel in the Installed Measurements
window.
b) Turn the 64V capacitive trimmer pot until the measured value is equal to Vrms 1 kHz