The Perkin Elmer pressure and vacuum cosine air pressure regulators. telescope on 31 October and 1 November 1989.

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Harvey Ray
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1 Check of Pressure and Vacuum Regulator The Perkin Elmer pressure and vacuum cosine air pressure regulators were removed from the f / 8 mirror cell while it was off the telescope on 31 October and 1 November They were brought to the second floor Optics Lab and mechanically fastened to the rotatory table in the lab. The pressure cosine regulator was tested first. With the regulator fastened to the rotatory table, the assembly was checked with the precision level when the vertical rotator indicated. The rotatory table was shimmed until the re ulator was leve to within ±.1" / foot. The pressure outlet of the gast pump was connected to the input of the pressure regulator so that filtered air was pumped through the regulator. Next the RAM inlet of a differential pressure gauge was connected to the outlet of the pressure regulator by a 'T' connector while the gauge's AMB inlet was vented to the atmosphere. The output of the differential pressure gauge was connected to a Fluke 77, 3~ digit, digital voltmeter. With the pump running, readings were taken with the differential pressure gauge in the RAM position and then in the AMB position. The RAM input was also disconnected from the regulator and the RAM and AMB positions read to monitor the zero point. This was done for sweep of the vertical axis of the rotatory table from +8 through to -8 at 5 intervals. Next the vacuum regulator was replaced for the pressure regulator and levelled. The input of the gast pump was connected to the output of the vacuum regulator. The differential pressure gauge

2 RAM input was connected to the regulator output with a 'T' connector and AMB input was connected to atmosphere. Again the readings were taken with the differential pressure gauge in both the RAM and AMB positions. The RAM input was disconnected from the regulator output and the RAM and AMB zero points taken. This was reported for the entire sweep of the vertical axis of the rotatory table from +8 to -8 every 5. Both sets of regulator data were taken twice with alternative data for a 9 set rotation of the regulator in the horizontal plane. Once the tests were finished, the regulators were re-connected on the f /8 cell. n the accompanying diagrams data is plotted RAM-AMB) versus rotation angle. Each plot has the two data sets separated by 9. A cosine function was fitted to the two sets of data and plotted as well. The difference ideal-measured) curves are also plotted. S. Hill J. Fellenstein

3 Pressure Regulator DATA * *.l.l.l *.l.l *.l * J RAM AMB RAM-AMB y DFF RAM AMB RAM-AMB y DFF S 8.92S S8S 2.S9 -.S 8.91S S7S 2.S8 -.S S SOS 2. Sll S S 2.SOl SO SO S2 -.2 SS 8. 77S S so S S S SSO SSO 2. lso S 6.S8 2.lOS S 6.S8 2.9S S SO SO 2.Sl S S S S S S 6.68S S S S SO S 1. 97S SOO S calculated values * y ACOSJ + B di ff RAM-AMB - 'Y.l is the regulator rotated 9 to the first position in the horizontal plane

4 ~ LO ~ u LO "... LO-'" _...~...,..._..,---.,...,...~~ Rotation Angle degrees)

5 t<) O "... Q Rotation Angle degrees) \

6 r tot) LO... " LO_._ Rotation Angle degrees)

7 ~... -o a..., - c Q) \... Q)O '+-q - '+-...,,... cno '+- '+- 1 ~ Rotation Angle degrees) <~

8 Vacuum Regulator DATA * * * 1. * J RAM AMB RAM-AMB y DFF RAM AMB RAM-AMB y DFF l calculated values * y ACOSB + B di ff RAM-AMB - y 1. is the regulator rotated 9 to the first position in the horizontal plane

9 '\ i. ~ -;. '~ "'- c ' ' '11. 'T'\ \/ ~~ '""- \ ~""" v ~\.)... -~ '~ '= ~~"'-!:-'~ ~ \)~ ,,.,.--. V! _.;...."'\, ' - -. ' ' \ LO ~ Rotation Angle degrees) 9.

10 ,, \\._ ";'\ \j ilo... t. '\.\. \.\-.. \; ~-j ~\ '\... \... "'.,_... ~ ':,!...,..._ '/~ ~-~ ~... \,_ ~ r \... i..,. \ 'J ~ c "''\~ -:: '.).. -lr \ ~ ~ ~ l.. ~\... ~ 6). t' 1 J _ ~ -.J. i Rotation Angle degrees)

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12 ,..._ L - ~ Rotation Angle degrees)

13 CALBRATON OF PORTABLE DFFERENTAL PRESSURE TRANSDUCER The calibration of the differential pressure transducer was done in the Waimea optics lab. The equipment used consisted of a water manometer, a Q_uke_ J~ _digi:t DYM, some 1/8" plastic hose and a 'T' with 1/8" hose fittings. Setup is as follows: one side of the U shaped manometer is left open to ambient pressure, the other side is connected to one side. of the 'T'. The other side of the 'T' is connected to the RAM port of the differential pressure box and the AMB port is left open to ambient pressure. The DVM fluke meter is connected to the BNC - - connector on the differential pressure box and its range is set to the 2 volt rang~. The valve on the differential pressure box is set to RAM and the box is turned on. The voltage is recorded for this condition of RAM on the high side and AMB on the low side of the pressure transducer. The valve is switch to AMB which reverses the connections to the pressure transducer placing the AMB on the high side and RAM on the low side of pressure transducer. Voltage is recorded for this condition and is then subtracted from the value obtained from RAM valve position. This is the differential measurement and should give a ZERO value when measuring the ambient condition since there should be no differential pressure drop across the RAM and AMB ports.

14 Next the ~ystem is checked for pressure leaks, this is done with the valve in the RAM position and air pressure of a few inches of H 2 applied to the tee junction. This is monitored by the manometer and the system is clamped at the point where the air pressure is being applied. When the system is closed off it should maintain its pressure for several minutes without giving any change in readings of the DVM or manometer. f it does, then all the system joints should be isolated and checked for leaks. Next, the calibration data is o~b -taki..ng a~ es of ~:r.emen.ts-o.lincreasing aj. pressure that is given by the total height displacement of the water columns in the water manometer and the voltage reading of the DVM at both the RAM and AMB valve settings. Note that each time the valve setting is changed, there is a small volume of air that is lost and must be made up to come back to the manometer reading. A data table is constructed to record the differential manometer reading, RAM voltage reading, ABM voltage reading and the calculated RAM-ABM) voltage. This data is then plotted in the form of RAM-ABM) vs pressure Slope is calculated from the graph to give the calibration constant of tne differential pressure box. This turns out to be 71. 5mV /in HzO.

15 Manometer differential RAM AMB Calculated Height H 2 o nches Valve Setting Valve Setting RAM-AMB) Volts DC Volts DC Volts DC o.oo File: 32-2

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