The NIKHEF MDT wire position meter
The following people made a positive contribution to this project:
| Design: |
Hans van Es |
| Construction: |
Mohammed Belkasmi |
|
Piet Wieten |
| Debugging and improvements: |
Sander Mos |
The wire position meter is based on work done by the University of Pavia
The first design was based on a report by the University of Pavia:
“An electromagnetic micrometer to measure wire location inside an ATLAS MDT drift tube”
by: Mario Gambiaghi, Alessandro Cardini, Roberto Ferrari, Gabriella Gaudio
This article by the Italians resulted in an improved design by Hans van Es.
Figure 1: outline drawing (PDF format)
The design is based on an IC from Philips, the NE5521 LVDT signal conditioner.
The chip include a low distortion, amplitude-stable sine wave oscillator, a synchronous demodulator and a output amplifier.
The sine wave oscillator drives a power amplifier who is coupled with the wire inside the MDT tube via a transformer. The frequency of the sine
wave is 235 Hz and the current through the MDT wire is approximately 50 mA.
The signal from the MDT wire is detected whith two pickup coils close to the end of the tube. This signal is amplified with a 50 dB pre-amplifier
along with a band-pass filter with a centre frequency around 235 Hz.
The signals from the sine wave oscillator and from the pre-amplifier are fed to the synchronous detector of the NE5521. The output of the
detector goes to a lowpass network. The DC output level of this network is 3 mV/micrometer.
The output signal goes to a display and to the MDT data acquisition system.
photos
| Photo readout cabinet |
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| Photo pre-amlifier |
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| MDT tube support with pre-amp |
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| MDT support |
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| MDT test overview |
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