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CERN-PH-DT1-GAS
Channel Flow Meters (and some other stuff)
Author: Jordan Michael Ziegler
Advisor: Mr. Steven Pavis
Thursday August 11, 2005
Some Hardware Needed
•PLC – Programmable Logic Controller
•Channel Flow Meter – Motherboard
•ELMB(s) (Embedded Local Monitor Board)
•PT100 Flow Cell Cables with Flow Cells
•CANbus Connection over network
•MODbus connection to main PLC
What is a channel flow meter?
• Made of two flow channels (PT 100s)
• Motherboard Flowmeter
• Daughterboard ELMB (radiation hard)
What does a channel flow meter do?
• Sends current through PT 100
• Measures voltages periodically
• Converts to flow
Measurement Procedure
I.
II.
III.
IV.
V.
Measure Ilow across Rref
Measure ambient temp. (To)
Measure Ihigh across Rref
Heat PT100 to To + ΔT
known current → voltage →
RPT100 → temperature →
slopes → flow
PT100 Flow Cell
FUNCTION BLOCK
What was my job?
• Set up sample gas system control
– Power up
– Establish communication
• Write a program to control measurement cycle
–
–
–
–
Establish communication and get slopes
Convert slopes to flow for one node (18 flow channels)
Expand to include 45 nodes simultaneously
Allow values to be read via MODbus
• Download to PLC and test
• Establish MODbus Connection via ethernet
• Upload calibration constants (LabVIEW) 45 x 2 x 18 x 11
= 17,820
• Document my work
S
T
R
U
C
T
U
R
E
D
T
E
X
T
A (very basic) program overview
for node 1
SET BITMASK
SEND RxPDO
START TIMER
TxPDO RECEIVED?
Emergency Message
Received?
NO?
Timer Expired?
NO?
YES?
Trigger fault bit
Write value “00000..” for flow
Reset timer
YES?
Trigger fault bit
Write value “00000..” for flow
Reset timer
YES?
Perform Calculations
Store flow values
Reset timer
Increment Counter
A few key things I learned
• PLC Programming
– Structured Text
– Function Block
• Industrial Communication Protocols
CANbus (CANopen protocol)
MODbus TCP/IP
• Computer Programming in General
• Physics of Gas Detectors
THANK YOU!!
•
•
•
•
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Dr. Homer Neal
Dr. Jean Krisch
Jeremy Herr
Steve Pavis
CERN PH DT1 GAS
All of You
•NSF
•Ford Motor Company
•CERN
•University of Michigan
Questions?