Quick Start Guide - DC1000A + HP / Agilent HP4284
Using the test leads that were supplied with your DC1000 and with your LCR meter, it is easy to setup your 4284A for testing any inductor under real DC bias loading.
The same advice also applies to the older DC1000 model.
SET-UP AND WARM-UP
As with any measuring equipment, allow both the DC1000 and your LCR to warm up for 30 minutes to ensure stable readings.
Enable the DC1000A by fitting your interlock system to the Interlock IN port on the rear of the unit, or use the Interlock Override plug provided with the unit.
Open circuit compensation
1 Remove any UUT (unit under test).
2 Try to keep all test leads in the same position as when the UUT is present.
3 Turn the DC1000A ON.
4 Set the DC1000A to 0.00A, using the rotary knob if needed.
5 Set DC1000A output to ON (press “output” button).
6 Leave the wiring set up like this and proceed to the next step.
B) Open circuit compensation on the HP4284A
1 On the HP4284A, press the MEAS SETUP button.
2 Use the soft keys to the right of the display to select CORRECTION (see right image).
3 Using the Arrow keys, move the cursor down to OPEN.
4 Press the soft key next to ON to enable the HP4284A open circuit correction.
5 Press the soft key next to MEAS OPEN and wait.
6 The compensation process can take 60-120 seconds, during which the HP will compensate over all frequencies.
7 At the end of this process the HP will display “OPEN measurement completed” at the right part of the screen.
Short circuit compensation
1 Fit a short between all leads. A bus bar or thick copper wire is ideal for this, as it will give good contact to all four clips. Try to keep all test leads in the same position as when the UUT is present.
2 Turn the DC1000A ON.
3 Set the DC1000A to 0.00A, using the rotary knob if needed.
4 Set the DC1000A output to ON (press the “output” button).
5 Leave the wiring set up like this and proceed to the next step.
B) Short circuit compensation on the HP4284A
1 Move the cursor using the arrow keys down to SHORT.
2 Press the soft key next to ON to enable the HP4284A short circuit correction.
3 Press the soft key next to MEAS SHORT and wait.
4 The compensation process can take 60-120 seconds, during which the HP will compensate over all frequencies.
5 At the end of this process the HP will display “SHORT measurement completed” at the right side of the screen.
Measuring under load
Once you have compensated the LCR for the leads and DC1000 you are ready to make measurements under load.
1 Turn the DC1000A output OFF.
2 Add your UUT back into the circuit, attempting to keep the test leads in the same position as when compensating).
3 Select the DC bias current you require using the rotary knob.
4 Enable the DC bias current by pressing OUTPUT.
B) Performing measurements
1 Press DISPLAY FORMAT on the HP4284A to return to the main screen.
2 Using the cursors move down to FUNC and select the parameters you wish to measure using the soft keys.
In this example we have selected Ls(Inductance) and Rs (Resistance).
3 Move the cursor down again to FREQ and then enter the frequency you require.
If using the number pad to enter a frequency, remember to press ENTER to accept the frequency.
Here we have selected 200Hz.
4 Move the cursor down again to LEVEL and enter the voltage required.
In this example we have selected 1.00 V.
5 Adjustments can be made to the DC bias level in real time with the DC1000 output enabled, and while the HP4284A is measuring, using the rotary knob on the DC1000A.
6 In our example (right image), the inductance at 0A DC bias is 12.29mH.
7 Once the DC bias level rises above the saturation point of the core, the inductance of the transformer drops (see right image, 512uH @ 3A DC).
BEST PRACTICE / REMINDERS
• DO NOT connect or disconnect the UUT or 4284A whilst the DC1000A is operating and ENABLED.
• Always remove the DC bias current by disabling the OUTPUT button before disconnecting either the UUT or the LCR
• Always try to keep all leads in the same position to improve the accuracy of the compensation, and hence the accuracy of your measurements
• For best performance at F>50 K Hz connect the earth socket on the front of the DC1000 with the earth socket on the LCR meter
• Consult your 4284A user documentation for more detailed instructions on compensation and general use.
If you see intermittent or constant "OVERLOAD" on LCR screen
This is basically a built in protection on the LCR
If it “sees” more than 2V across its own terminals it reads overload.
This will be a combination of :
A) AC volts drop - caused by the LCR V AC settings and the resulting AC drop across the UUT (X=2 x PI x F x L)
B) DC volts drop - caused by the DC Amps from the DC1000 and the resulting V drop caused by the DC resistance on the UUT.
1) Check for good connections as any poor contacts or underrated test leads can give a small contact resistance that could mean bigger V DC drop at larger Amps.
2) Check the DCR of your UUT is suitable.
3) Check if reducing the LCR VAC reduces the combined V enough to remove the OVERLOAD
4) Check you have DC ISO= ON and ALC =ON in LCR settings