Calibrating the LCR Meter

Overview

Open and short calibration ensure that the LCR Meter reads the proper impedance at two extremes: during a virtually zero capacitance (two parallel plates set apart [open calibration]) and during a near zero resistance (two parallel plates in contact [short calibration]).

Perform the open and short calibrations once a day when using the dielectric accessory.

Calibrating the LCR Meter

The calibration procedures below pertain to the Agilent E4980A LCR Meter (hereafter referred to as the LCR Meter). Only the LCR Meters Agilent 4285A and E4980A are supported. TRIOS software automatically recognizes the LCR Meter when connected to the PC and switched on. Only when the LCR Meter is detected, calibration is enabled.

TRIOS software includes an automated and a manual calibration procedure. The manual calibration allows the calibration from the LCR Meter front display without disconnecting the LCR Meter. The automated procedure calibrates the LCR Meter via TRIOS; the LCR Meter remains in control of TRIOS and cannot be operated from the LCR Meter front display.

Before calibrating the LCR Meter, verify the following:

• The LCR Meter is connected to a USB port on the PC
• The LCR Meter is powered on
• The status bar of the TRIOS software displays LCR Meter: Enabled

From the File Manager, select Calibration> Accessories> Dielectric. Then select either Use calibration wizard or Manual calibration.

• NOTE:
• Rotation of the shaft is limited to 1 full rotation during dielectric tests to avoid winding up the cable connecting the BNC junction box with the upper dielectric test geometry.

• It is recommended to lock the bearing (middle button on the test station keypad) before starting the calibration to avoid accidental rotation of the shaft

• In order to avoid trapping of the upper sleeve/cable when closing the oven doors, route the sleeves through the clip on the upper BNC junction box. Do not wrap the cable around the clip, this would prevent the cable from disengaging in case of accidental shaft rotation.

Manual Calibration

Press the Calibration button. A message displays, instructing you to use the Local/Lock key on the LCR Meter to set the LCR Meter into local control. The LCR Meter is reset and a Processing message displays on the LCR Meter front display. Proceed as follows:

Open Calibration

1. From the instrument Gap Control panel, perform Zero Fixture.
2. Set the gap to 25 mm and close the ETC doors.
3. On the LCR Meter front panel, press Meas Setup (to the left of the numbered keypad).
4. From the LCR Meter screen, select CORRECTION.
5. Using the LCR Meter directional keypad, scroll to CABLE and select 2 m.
6. Using the LCR Meter directional keypad, scroll to OPEN and select On.
7. With the cursor still highlighting OPEN, select Meas Open from the LCR Meter screen. A OPEN measurement in progress message displays.
8. When the calibration is complete, press Display Format on the meter front panel. Confirm the following value: Cp < 0.01pF.

Short Calibration

1. From the instrument Gap Control panel, command a zero gap to bring the two geometry plates together and apply 5 N to 10 N (500 gm to 1000 gm) of force from the instrument Axial Force Control panel. Disconnect the test fixtures from the BNC junction box and short the upper and lower junction box with the short cable supplied.
2. On the meter keypad, press Meas Setup.
3. From the LCR Meter screen, select CORRECTION.
4. Using the LCR Meter directional keypad, scroll to SHORT and select On.
5. With the cursor still highlighting SHORT, select Meas Short from the LCR Meter screen. A SHORT measurement in progress message displays.
6. When the calibration is complete, press Display Format on the meter front panel.
7. Change the display functions:
1. Using the LCR Meter directional keypad, scroll to FUNC.
2. Select Cp – ...►.
3. Select Cp – Rp.
4. Verify the following value: Rp < 2W.
5. Select Cp – D when finished verifying the value in step d.

• NOTE:
• The calibration routine proposes to use a short cable to perform the ‘short’ calibration. The reasons are contact issues due to alignment and residual deposits on the surface of the plates. Instead of shortening the BNC junction boxes, the plates can stay connected and included in the short process. In this case the plates have to be absolutely clean (clean with a solvent and brass brush if necessary) and aligned. It helps to rotate the upper plate a fraction of a degree to improve the contact.
• The difference between using the short cable or shortening the plates directly is small. It is therefore recommended to use the short cable to avoid a bad short calibration with an artificial high resistance, which would corrupt the test results.

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Automated calibration

1. Select the Use calibration wizard option button to enable the automated calibration. Make sure that the dielectric test fixtures are installed and connected to the BNC junction boxes.
2. Close the ETC doors and press the Calibration button. The text Resetting the meter – Please wait displays. At the same time, a Processing message is shown on the front display of the LCR Meter.
3. When finished, the text changes to Performing open measurement – zeroing the gap. The gap is zeroed automatically, and the upper plate is positioned at a gap of 25 mm. The text changes to Performing open measurement and an Open measurement is performed. An OPEN measurement in progress message displays on the LCR Meter display.
4. When finished successfully, an Open calibration result message displays in the calibration tab with the correction value (~1 e^-10 µF) and a green check mark.
5. The information text changes and instructs you to disconnect the cable from the upper and lower test fixtures and shorten the upper and lower BNC junction boxes with the short cable supplied.
6. Press Continue to perform the short measurement. The text changes to Performing short measurement.
7. The plates are now brought together and a compression force of 5 N is applied. The Short calibration is performed. A SHORT measurement in progress message displays on the LCR Meter display.
8. When finished successfully, a Short calibration result (uncorrected) message displays in the calibration tab with the correction value (~100 mW), and a Short calibration result (corrected) message displays in the calibration tab with the correction value (~50 mW). A green check mark indicates a successful calibration. If the short calibration is not performed successfully, a red X displays. Use the Repeat button to redo the Short calibration.

• NOTE:
• The calibration routine requires use of a Short cable to perform the Short calibration because of contact issues due to alignment and residual deposits on the surface of the plates. Instead of shortening the BNC junction boxes, the plates can stay connected and included in the short process. In this case the plates have to be absolutely clean (clean with a solvent and brass brush if necessary) and aligned. It helps to rotate the upper plate a fraction of a degree to improve the contact.

• The difference between using the short cable or shortening the plates directly is small. It is therefore recommended to use the short cable to avoid a bad short calibration with an artificial high resistance, which would corrupt the test results.

• The Cancel button can be used at any time to abort the calibration.

9. After the Short calibration has been performed successfully, and the Short cable has been used, remove it and reconnect the upper and lower BNC junction box with the test fixtures. Then press Continue.

10. The upper plate is now positioned at a gap of 1 mm and a confidence check is performed. The results display in the calibration tab. The capacitance (Cp) should read between 4.2 to 4.7 pF for the 25 mm dielectric test fixtures. The dielectric loss (D) should be less than 0.01.

• NOTE: If the disposable plate holder is used, the capacitance for the 1 mm gap is different and will depend on the type of disposable plates used.

11. When the confidence check has been performed successfully, leave the calibration wizard by hitting the Finish control button.

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Calibration Confidence Check

Once the LCR meter is calibrated, perform the following procedure to ensure that the calibration was successful. If a short cable has been used, remove it and reconnect the upper and lower test fixture to the corresponding BNC junction box.

1. From the Instrument gap panel, perform Zero Fixture.
2. Set a gap of 1 mm.
3. Verify the following values:

• Capacitance (Cp) should be between 4.2 to 4.7 pF for the 25-mm dielectric plates.
• DE loss (D) should be less than 0.01.
• NOTE: If the disposable plate holder is used, the capacitance for the 1 mm gap is different and will depend on the type of disposable plates used.

On the Calibration page select Finish to complete the manual calibration. The LCR meter is switched back to remote control.

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