8700 SERIES. narda OPERATION MANUAL DIGITAL METER CALIBRATION FIXTURE. Safety Test Solutions P/N an L3 communications company

Transcription

1 8700 SERIES DIGITAL METER CALIBRATION FIXTURE OPERATION MANUAL narda Safety Test Solutions an L3 communications company P/N

2 narda Safety Test Solutions an L3 communications company USA: 435 Moreland Road Hauppauge, NY Tel Fax GERMANY: Sandwiesenstr 7 D Pfullingen Tel Fax support@narda-sts.de

3 Introduction The P/N calibration fixture is comprised of a cable with a connector that replicates a Narda 8700D series probe, a channel selector switch, input jacks for a separate power supply, and test jacks. A fuse and a zener diode are used to protect the meter from the accidental application of incorrect or reverse polarity voltages. This fixture is used to check that calibration of Narda 8700 Series Meters and to provide simple access to a meter s operating voltages. Theory of Operation The Narda 8700 Series of radio frequency radiation instruments is comprised of meters, probes, cables and fiber optic links that can be used in many different configurations to measure electric and magnetic fields. The system is modular with all components individually calibrated. The amplifiers in the handle of every prove are adjusted during the calibration process to provide the same DC output voltage at full scale. Every meter has two input channels a linear input and a nonlinear or compensated input. Full scale for linear output probes is equal to volts DC. Certain probe models have a somewhat non-linear response which is compensated for within the meter. Ultra-wideband probes those with a frequency response of 300 khz to GHz contain two different sensors. These probes utilize a twochannel amplifier one with a linear output and the other with an non-linear output. Application This calibration fixture can be used to check the calibration of all Narda 8700 series digital meters. The list of currently applicable meter models are: Models 8718 and 8718B Model 8715 Model Series 3

4 These digital meters do not have potentiometers that require periodic adjustment. The purpose of this calibration fixture is to provide a convenient means to apply a precise DC voltage to each of the meter s two input channels to confirm that the meter is functioning properly. A specific input voltage on each channel should provide a specific indicated measurement which is dependent on the probe model that the meter is set for. The calibration fixture also provides access to the operating voltages within the meter. These voltages can be checked to provide another indication that the meter is operating properly. Equipment Required The only equipment required in addition to the meter(s) to be checked are: An accurate, stable low voltage power supply. An accurate DC voltmeter Model cable, as required to connect the meter to the test fixture. Using the Calibration Fixture To use the calibration fixture: 1. Turn on the power supply and adjust it to approximately zero volts. Turn the power supply off and connect it to the two terminals on the top of the fixture. Make sure that the polarity matches the label for REF GND (reference ground) and V. 2. Connect the calibration fixture to the meter. The connector on the fixture plugs directly into meter Models 8712, 8715 and 8718B. A probe extension cable (Model ) is used to connect to the Model 8718 Meter and the 8717 Series Meters. 3. Set the toggle switch on the fixture to the CH A (channel A) position. 4. Turn the meter on. 4

5 5. On the Models 8718, 8718B and 8717 Series Meters set the meter to the model 8741D. On the Models 8712 and 8715 Meters, set the meter to the 20 mw/cm 2 range and for electric field probes. Note that the Model 8741D probe contains two sensors and uses a dual channel amplifier. NOTE The meter is now ready to be zeroed. However, the calibration fixture does not exactly replicate the probe and this test configuration will fail the normal criteria for zeroing a probe. Therefore, it is necessary to force a zero. This capability has been built into all the Narda 8700 Series Digital Meters. 6. Turn on the power supply and adjust the voltage at the terminals of the calibration fixture to V ±5 mv. 7. Force a zero on the meter (see Forcing a Zero on page 6). 8. Readjust the power supply to V ±5 mv. 9. Read the field strength on the meter. It should indicate 10 mw/cm 2 ±0.3 mw/cm 2. This is the linear input channel. 10. Move the toggle switch on the fixture to the CH B (channel B) position. 11. Read the field strength on the meter. It should indicate 12.5 mw/cm 2 ±0.375 mw/cm 2. This is the non-linear or compensated input channel. Updating the Calibration Date The meter is accurate within specifications providing that indicated field strength in steps 10 and 12 above are within the tolerances indicated. If the meter is operating properly with specification, the calibration date can be updated to the date it was checked using this fixture. 5

6 If the meter is not operating within specification, it should be returned to Narda for service. To update the calibration date on the Models 8712 and 8715 Meters: 1. Remove the old calibration label on the bottom of the meter. 2. Adhere a new calibration label to the bottom of the meter. Write in the calibration date. To update the calibration date on the models 8718, 8718B and 8717 series meters, it must be done electronically using the interface software supplied with the meter: 1. Connect the meter to a personal computer that has the interface software installed and establish communications using the procedures described in the meter operations manual. 2. Select Read Meter Data from the pull down menu under Diagnostics. 3. A screen will appear that states Read Any Meter Data. At this point type >CAL then press Enter on the computer. 4. A prompt will appear that states Type Cal Month. Type in a two digit number representing the month of calibration and press Enter on the computer. 5. A prompt will appear that states Type Cal Day. Type in a two digit number representing the day of calibration and press Enter on the computer. 6. A prompt will appear that states Type Cal Year. Type in a two digit number representing the year of calibration and press Enter on the computer. 7. A prompt will appear that indicates the calibration date that you have entered and gives three choices: Yes (Y) confirms that the date is correct and places the date in the meter s memory. No (N) is used to enter a different date. 6

7 Quit (Q) is used to quit the calibration update portion of the interface software without entering a date. Forcing a Zero To force a zero on the Models 8712 and 8715 Meters: 1. Once the probe full scale measurement range and the field type have been entered and the word ZERO is flashing on the display, press the Auto Zero key as in normal operation 2. Within five seconds after pressing the Auto Zero key, press the Range key to force a zero. 3. The meter should almost immediately indicate that it has been zeroed. The ZERO indicator will no longer be flashing and the meter will be reading either zero or a very low level. To force a zero on the Models 8718, 8718B and 8717 Series Meters 1. Once the probe model has been entered and the screen indicates that the meter is ready to be zeroed, press the Auto Zero key as in normal operation. 2. Numbers will be displayed below the ZEROING prompt several seconds after pressing the Enter key. Press the 8 key for about two seconds immediately after these numbers appear. 3. The meter should indicate that it has been zeroed within about five seconds. Checking Operating Voltages The calibration fixture provides access to the operating voltages within the meter. These voltages can be checked to provide an increased level of confidence that the meter operation is completely normal. 7

8 The four operating voltages that can be checked are available via test jacks on the sides of the calibration fixture. These four voltages and the acceptable operating ranges are: Description Range +V os 0.0 V ±0.5 mv to +2.4 V ±0.5 mv -V os 0.0 V ±0.5 mv to -1.4 V ±0.5 mv +5 V V ±0.25 V -5 V V ±0.25 V To measure the operating voltages of the Narda 8700 Series digital meters: 1. The ±V os voltages are measured while the meter is zeroing. Connect a Digital Volt Meter (DVM) between the +V os jack and ground and set the range for millivolts. Turn the 8700 Series Meter off and on. Select a Model 8741 Probe (or a 20 mw/cm 2, E-field probe) and begin zeroing the meter. Observe and record the maximum and minimum voltages. 2. Connect a Digital Volt Meter (DVM) between the V os jack and ground and set the range for millivolts. Turn the 8700 Series Meter off and on. Select a Model 8741 Probe (or a 20 mw/cm 2, E-field probe) and begin zeroing the meter. Observe and record the maximum and minimum voltages. 3. Measure and record the +5 V and 5 V power supply voltages. narda Safety Test Solutions an L3 communications company USA: 435 Moreland Road Hauppauge, NY Tel Fax NardaSTS@L-3COM.com GERMANY: Sandwiesenstr 7 D Pfullingen Tel Fax support@narda-sts.de 8