Transcript LabVIEW Based Test and Calibration System for

1.
Commissioning of cryogenic crates using Mobile Test Bench
1.
2.
3.
2.
The Mobile Test Bench
Cryogenics crates and equipment – types of transducers
and actuators
Electrical tests - instrument, cable & card tests
Test and calibration systems for pressure sensors
1.
2.
Low pressure bench
High pressure bench
The Mobile Test Bench (MTB) was a custom Automatic Test Equipment system,
designed for operation in the LHC tunnel. Its purpose was to perform the final test
of the cryogenic FIP crates and their attached sensors and actuators.
Need of automatic system for testing of the cryogenic
acquisition electronics

Large amount of devices to be tested in relatively short time
Synchronization with main database for retrieving the crates
configuration
Internal automatic signals routing between device under test and
testing equipment simplifying operators actions, reducing test duration
FIP BUS
Tunnel
cables
FIP CRATE
Sensors/actuators
Mobile Test Bench based on PXI
CPU
MTB test
cables
Connectors
panel


DMM1
MATRIX for
signals
routing
DMM2
Current
generator
Resistance
simulator
MTB was based on the PXI platform by
National Instruments
The PXI rack houses:
1.
A controller by NI running on Win XP
2.
Two FIP communication cards
3.
A 276 x 8 matrix module by Pickering
4.
One programmable resistor module by
Pickering
5.
Power supply card
6.
Multimeter card
7.
GPIB interface
Apart from PXI, other components are:
1.
Keithley 2400 SourceMeter
2.
Keithley 2182 NanovoltoMeter
3.
A connector panel
4.
One UPS
Types of cards and transducers:
1.
DI – valve card
2.
TT/PT/LT cards – temperature, pressure and level transducers cards
3.
FIP card – each consist of 2 FIP agents (left for sensors and right for actuators)
4.
EH cards – electrical heaters cards
Purpose of the tests was to verify that each instrument:
1.
was physically present at the machine
2.
was correctly wired and properly connected
3.
had the expected resistance value
Temperature transducer TT
 Two types: CERNOX and Pt100
 pinout: subD 9 (M) and fisher 12 (M)
 4-wire resistance test
 Resistance between U+ and I+

Pressure transducer PT
 Types: 20 bar, 4 bar, 350 mbar
 pinout: subD 9 (M) and 6 MIL (M)
 4-wire resistance test
 Resistance between U+ and I+
 Resistance on Pt1000
 Short circuit against the ground

Level transducer LT
 Probes lengths: 150mm, 400mm, 600mm
 pinout: subD 9 (F) and 4 MIL (M)
 4-wire resistance test
 Resistance between U+ and I+
Helium level
Pressure
Temperature

1.
to track down every electrically measurable error within a cable instrument assembly. (open or inverted connections, short circuits and low
insulation resistance values)
2.
MTB measured the resistance between all pin combinations of a cable
connector and the resistance between each pin of the connector and
ground
3.
In principle, only measurements between active pins (U+, U-, I+, I-) that
belong to the same sensor produced relatively low resistance values. All
other combinations implied an open circuit (any resistance value above
1MOhm was considered open circuit)
to validate the correct functionality of each electronic card of the crate.
TT/PT card example
1.
TT/PT cards are able to measure TT or PT
2.
TT/PT cards measure the attached sensor using the 4 wire method
3.
CERNOX resistance ranges from some ohms at ambient temperature to tens of
kOhm at cryogenic temperatures. TT cards have 3 measuring ranges:
1.
2.
3.
30 – 300 Ohm (excitation current 100uA)
300 – 3 kOhm (excitation current 10uA)
3k – 30 kOhm (excitation current 1uA)
TT card test consist of 9 set-points
3 for each range
Measurement procedure:
1.
2.
3.
4.
5.
6.
The setpoint resistance is set in the programmable resistor module.
The matrix connects the resistance to the MTB instrumentation (Keithleys ).
The Keithleys perform a measurement of the resistance (Bench Measurement).
The matrix disconnects the resistance from the Keithleys and connects it to the
TT card under test through the MTB cable that is plugged to the crate card.
The TT card performs measurements of the resistance (multiple times per
second). MTB acquires measurement data through FIP (FIP Measurement).
MTB software compares the two values (Bench Measurement and FIP
Measurement). The step is marked as “OK” if the relative error is less than 0,3%.
Low pressure bench – on the right
Climatic chamber (temperature module of pressure bench) – on the left
LPB is based on the PXI platform by
National Instruments
The PXI rack houses:
1.
An embedded controller by NI
running on Windows XP
2.
Multimeter card
3.
GPIB interface
Apart from PXI, other components are:
1.
Two pressure gauges with different
ranges allow to perform high
accuracy tests from near 0mbar to
130mbar
2.
PLC controller for controlling four
electromagnetic valves
3.
Three pumps (one is turbomolecular
pump)
4.
5 DMM’s
5.
Power supply system
Software:
1.
LabVIEW for controlling all system;
modular structure for reusability in other
projects (temperature, pressure, PID,
2.
sequencer)
MatLab for data analyses
HPB is based on the PXI platform by
National Instruments
The PXI rack houses:
1.
An embedded controller by NI
running on Windows XP
2.
Multimeter card
3.
GPIB interface
Apart from PXI, other components are:
1.
Two pressure gauges with different
ranges allow to perform tests - from
pressure near 50mbar to 20bar
2.
Three electromagnetic valves
3.
Pumps and bottle with synthetic air
Software:
1.
LabVIEW for controlling system