Aetna test is the brand leader of detech / keysight. In the early days, it was called HP / HP. Around 2000, after the separation of civil products and testing, it was changed to Agilent (electronics, medicine, chemical analysis). At the end of 14, the name of Electronics was changed to Shide technology. Of course, the price of the German series of electrical measuring instruments is not cheap, at least tens of thousands, hundreds of thousands of precision instruments; therefore, it is necessary to use them according to the correct process, and calibrate the instruments regularly.What problems should be paid attention to in the calibration process of Shide series instruments?
1、 Calibration procedure of spectrum analyzer
There are three common calibration procedures in the internal computer of the instrument: frequency calibration, amplitude calibration and YTF calibration.
1. Frequency calibration
When the spectrometer is vibrated, transported, placed for a long time or the ambient temperature changes greatly, the frequency tuning of the spectrometer will change, resulting in the frequency measurement error. In serious cases, the measurement signal will shake left and right, which can be eliminated by frequency calibration. The calibration process is mainly to calibrate the scanning time, center frequency, span (sweep width), YIG main coil delay, sub coil sensitivity and sweep sensitivity of the spectrometer with 300MHz signal as the reference signal, so that the frequency tuning range of the spectrometer is normal.
The calibration signal (CAL output) is connected to the signal input terminal of the spectrometer by using the frequency / amplitude calibration cable. Press [cal] [calfreq] to enter the frequency calibration program. After the calibration, the “caldone” message will appear on the screen. Press the [calstore] key to store the calibration data in the E2PROM of the instrument.
2. Amplitude calibration
As with frequency calibration, when the accuracy of the spectrum analyzer changes, the instrument can meet the factory index through the amplitude calibration program. The process is mainly to measure and correct the error of the whole channel amplitude, resolution bandwidth filter, logarithmic amplifier, input attenuator and other amplitudes of the spectrum analyzer with 300MHz signal as the reference signal.
The calibration signal (CAL output) is connected to the signal input terminal of the spectrometer by using the frequency / amplitude calibration cable. Press [cal] [CalAmp] to enter the amplitude calibration program. After the calibration, the “caldone” message will appear on the screen. Press the [calstore] key to store the calibration data in the E2PROM of the instrument.
3. Pre selector (YTF) calibration
The frequency sweep and tracking of preselector is the key to the harmonic band of spectrometer. The driving circuit independent of the first LO is used to calibrate and drive each band. The hysteresis and delay of the first oscillator and preselector are compensated in the fast scan, slow scan and cross band scan of the spectrometer, which greatly improves the tracking characteristics of YTF. If the spectrum analyzer has 5dB or more amplitude error in the harmonic band, it is often caused by the instrument’s long storage time and large environmental temperature change. If the preselection tracker is not good, it will cause amplitude measurement error, or even can not measure the signal. At this time, YTF calibration should be carried out.
Using YTF calibration cable, connect 100 MHz comb wave (comb) signal to RF input of spectrometer. Press [cal] [calytf] to enter YTF calibration program. After the calibration, the “caldone” message will appear on the screen. Press the [calstore] key to store the calibration data in the E2PROM of the instrument.
If there is an error signal when exit or calibration cannot be completed during calibration, press [calfetch] to retrieve the calibration data. The instrument will need to be readjusted and repaired.
2、 Calibration data of spectrometer after calibration
Hp859x series spectrum analyzer can not only calibrate various indexes of the instrument, but also store various calibration data in memory, which is convenient for operation and maintenance personnel to refer to. As long as you enter the maintenance menu, you can display the calibration data.
Press the menu [cal] (more) (servicediag) (displaycaldata), then the amplitude calibration table of the spectrometer will be displayed on the screen.
The table contains the amplitude error correction values of input attenuator (rfatn) in steps of 0-70db and 10dB, log amplifier (log) in steps of 0-50db and 10dB, Lin amplifier in steps of 10-40dbm and bwamp in bands of 1, 3 and 10 The width is the amplitude error correction value of each step; the gain correction value of the whole channel of the spectrometer is expressed in the form of DAC, the minimum correction value is 0, the maximum correction value is 255, etc.
Through the amplitude calibration table, we can not only analyze the performance index of each hardware circuit in the spectrometer, but also bring some convenience to the maintenance of the instrument. The maximum amplitude correction ability of the internal computer of the spectrometer is ± 2.2dbm, and the maximum DAC correction value is 255. If the amplitude correction value of the spectrometer exceeds ± 2.2dbm, and the maximum DAC correction value is 255, the calibration cannot be completed, and the error message will appear on the spectrometer screen.
Editor in charge: GT