Specifications

Doc Number: VIS-ANA-VER-01001-9002
Date: 27 May 2004
Issue: 5.0
Page: 51 of 80
Author: J. Delgadillo
Controls Preliminary Design Report Issue 5.doc
4.2.5.12 Data Acquisition System
The Data Acquisition System is comprised of the Data Acquisition Unit, 25 VertexRSI
provided RTDs (AD01 6.4.5a spec) and conditioning modules for VISTA provided 15
additional temperature sensors (AD01 6.4.5c & d spec). 5 of these sensors will be located on
the structure while the remaining 10 will be placed on the M1 mirror. It is assumed that the
same type of conditioning modules will be used for the VISTA provided sensors as the ones
used for the VertexRSI provided temperature sensors (100 ohm RTDs). The Data
Acquisition Unit will reside inside the mount Yoke and will interface via the CANOpen
protocol to the M1 Mirror Support LCU.
The RTDs to be provided by VertexRSI are a 3-wire platinum RTD manufactured by
Pyromation, Inc having part number R3T1853RB1-F3B006-6. The 100 ohm platinum RTD
(AD01 6.4.3 spec) has a temperature coefficient of 0.00385 and an accuracy of +/- 0.03% @
0°C. For the operational temperature range of 0 to 15 °C, the corresponding accuracy of the
RTD would be 0.08 to 0.10 °C. The location of the 25 VertexRSI Provided RTDs will be as
follows:
OSS Spyder 4
OSS Ring 2
OSS Tube 6
ALT Ring 4
ALT Bearing 2
Mirror Strt 3
Outside Pier 2
Inside Pier 2
As requested by VPO, VRSI is planning on using Beckhoff CANOpen hardware for the Data
Acquisition Unit. The Beckhoff RTD modules have a published measurement accuracy of +/-
1 °C over the entire measurement range of – 250 °C to 850 °C. The RTDs to be provided
have a temperature range of –200 to +200 °C, thus the Beckhoff measurement error would be
reduced to approximately +/- 0.4 °C. Conversation with Beckhoff seems to indicate that the
published 1 °C accuracy number is too conservative and that typical values are in the order of
0.5 °C, thus, for our temperature range, the measurement error would be approximately +/-
0.2 °C. This accuracy would be for the un-calibrated measurement, thus calibration of the
measurement would yield accuracy values closer to the AD01 6.4.3 0.1°C accuracy spec.
Since the Mount Control System is not required to obtain the temperature information, the
M1 Mirror Support LCU would be responsible for the calibration of the RTDs.
Vista has exercised the M1 mirror LVDT option, thus six of the M1 mirror sensors will
become the AC LVDTs. The last four sensors would remain the RTDs. AC LVDTs were