Pressure Transducer Field Installation Instructions for the LI-6252 CO 2 and LI-6262 CO 2 /H 2 O Analyzers

Transcription

1 Pressure Transducer Field Installation Instructions for the LI-6252 CO 2 and LI-6262 CO 2 /H 2 O Analyzers Please read these instructions before beginning installation. Please note that the analyzer s auxiliary input channel will be used to measure the raw mv output of the pressure transducer; after installation the input will therefore no longer exist (see Step 11). If you have any questions please contact LI-COR for assistance. Follow these steps to install the Pressure Transducer: 1 Examine contents of the bags. You should find the following items: : Silicone lubricant 7/64 hex key Modified 1/4 nut driver Bev-a-line tubing (2 feet) : Pressure Transducer (encased in white foam). Mounting bracket (part number ). Pressure sensor adapter board (part number ). Nickel plated manifold (part number ). Two manifold mounting clips (part number ). Two black /2 socket head screws (part number ). Two O rings (part number ). 4 5/8" length of urethane tubing /4" machine screw (part number ). Calibration data sheet with a serial number that matches the label on the mounting bracket. Tools required: Phillips head screwdriver, crescent wrench, knife. Tape 5-pin connector 5-pin pressure transducer cable connector Ground lug 10-pin connector Foam LK1 P2 TP1 P2 To IRGA digital board circuit board 8-pin connector Figure pressure transducer assembly parts (l.-r., pressure transducer, mounting bracket, manifold, pressure sensor adapter board). 2 Remove instrument cover. Remove the 8 screws on the top and 4 screws on the bottom of the cabinet. The bottom 4 screws are located opposite the rubber feet, at the outer edge of the enclosure. Slide the cover off to either the front or back of the instrument. 3 Remove the nuts from the Sample In and Reference In fittings that are on the outside of the back panel. You may need to hold the nuts on the inside of the back panel to loosen the external nuts. Do not remove the internal hoses that are connected to the fittings. Note the position of the two inlet fittings, and pull them through the back panel with the hoses attached.

2 4 Mount the pressure transducer to the inside back panel of the instrument (Figure 2). Insert the transducer foam block assembly into the mounting bracket so that the pressure transducer hose connection pipe is below the bracket, and is facing toward the front of the instrument. The top of the bracket should be flush with the top of the pressure transducer assembly. Fit this assembly between the two holes where the air inlet fittings were removed. Slide the fittings through the mounting bracket holes and the back panel. Install the fitting nuts and tighten. You may need to hold the nut on the inside as you tighten the outside nut. Air inlet fitting Mounting bracket assembly SAMPLE REFERENCE IN Hose connection pipe Figure 2. Fit transducer assembly between Sample and Reference In fittings. 5 Route the pressure transducer wires to the front of the instrument. The wires from the pressure transducer should pass between the internal Sample In and Sample Out fittings. Thread the wires under the RS-232 ribbon cable and down to the bottom of the instrument enclosure. Tuck the wires under the existing cables and run them toward the front panel (behind the keypad). You can then tuck them under the two circuit boards. You may need to uncoil the pressure transducer wires a few turns to get them to slip under the circuit boards. 6 Install pressure transducer adapter board. Locate the large circuit board that is parallel to and immediately behind the instrument front panel. This is the digital board. There are two black plastic connectors on the top right corner of the board (nearest the keypad); one has 10 wires leading away from it, and the other has 8 wires (Figure 3). Note the orientation of the two connectors, and unplug them by pulling straight up. These connectors plug into the adapter board; the board s function is to power and accept the input from the pressure transducer board. Adapter board Connectors Yellow Purple Digital board connector Figure 3. Location of digital board and connectors. Figure 4. Note orientation of connectors and invert.

3 7 Invert the connectors, so the holes that plug into the adapter board face up instead of down (Figures 4 and 5). Make sure that you do not turn any connectors around when you plug them into the adapter board, as serious damage to the instrument could result. The wire colors as viewed from left to right do not change. Orient the adapter board so that the pins are facing down, and the ground lug is facing toward the center of the instrument. Plug the two connectors into the adapter board and insert the female connector on the adapter board onto the pins on the IRGA digital board (Figure 6). Plug the pressure transducer cable into the adapter board. Note that there is a locking ridge on the pressure transducer cable female connector that will engage another ridge on the male half of the connector on the adapter board. Ground lug Adapter board Figure 5. Invert the connectors. Figure 6. Plug connectors and adapter board onto digital board. 8 Attach the ground lug to the IRGA mounting bracket. Use the /4" screw to attach the ground lug to the IRGA board mounting bracket (Figure 6). 9 Look for the pressure transducer manifold. Manifolds were factory installed beginning with LI-6251 serial number IRG1-308, LI-6252 serial number IRG2-305, and LI-6262 serial number IRG3-572, and were installed on all instruments returned to LI-COR for any reason after February 1, The manifold is attached to the end of the gold plated optical cell (Figure 8). If the manifold is already installed, proceed to Step 13. If the manifold is not installed, proceed to Step Remove hose barbs from optical cell. Before starting, be sure that the inside of the enclosure is clean and free of dust; we recommend blowing it off with compressed air before disconnecting any hoses. Locate the Sample Out and Reference In ports on the back panel of the instrument. Follow the hoses which are attached to these ports inside to where they attach to the gold-plated IRGA optical cell. Cut the hoses at the optical cell, as close to the barbs as possible. We recommend that you flow air through the optical cell so that there is flow of 3-10 lpm coming out of the hose barbs that are to be removed. This will prevent debris from falling into the optical cell when the barbs are removed. Connect a T fitting ahead of the Sample In and Reference Out fittings, or do them one at a time, switching the flow to the cell whose barb you are removing. Use the modified nut driver provided to unscrew the two hose barbs. Note that the nut driver may not fit over the barb completely until the barb has been rotated a few degrees. Use a dust free cotton swab to remove any dirt or debris that may be next to the tapped holes where you removed the hose barbs.

4 11 Install manifold onto optical cell. Insert one of the black 6-32 socket head screws through the hole in the narrow end of the manifold and thread it into one of the manifold mounting clips about 1 1/2 turns. Apply a thin film of the silicone grease provided to both surfaces of the O-rings. Place the two O-rings into the counterbored area on the bottom of the manifold; the grease will help hold the O- rings in place while you install the manifold. Hook the mounting clip under the lip of the optical cell and position the manifold over the holes in the optical cell. Tighten the screw just enough to hold the manifold in place. Insert the other socket head screw through the manifold. Hold the second mounting clip with a pair of long nose pliers under the lip of the optical cell and thread the screw into the clip. Alternately tighten both screws so that there is even pressure on both sides of the manifold. Mounting clip To pressure transducer O-rings Figure 7. Manifold and mounting clips. 12 Connect the hoses to the manifold. Insert the 4 5/8 length of urethane hose onto the single hose barb on the side of the manifold (the manifold surface perpendicular to the optical cell). Attach the other end to the metal pipe protruding from the pressure transducer assembly. Make sure that the hoses leading from the Sample Out and Reference In fittings are cut cleanly, and that they are long enough to reach the barbs on the top of the manifold. If they are too short, replace them using the Bev-a-line tubing included. Attach the hoses to the manifold. The hose connected to the Sample Out fitting attaches to the hose barb that is closest to the IRGA back panel. Push the hoses onto the barbs as far as they will go, until they touch the hex nut portion of the hose barb. The finished assembly should look similar to that shown below in Figure 8. Figure 8. Finished assembly.

5 13 Connect transducer to manifold (for manifolds that are factory installed). Use the modified nut driver provided to remove the 1/4 hex head plug from the manifold on the sample cell output (nearest the IRGA back panel). Remove a hose barb from the extra manifold included in the pressure transducer kit and install it in place of the plug. Insert the 4 5/8 length of urethane hose onto the single hose barb on the side of the manifold (the manifold surface perpendicular to the optical cell). Attach the other end to the metal pipe protruding from the pressure transducer assembly. The finished assembly should look similar to that shown in Figure Configure the software. Turn the analyzer on. Press FCT 77 and enter 0. Press FCT 71 and enter coefficient a from the pressure transducer calibration sheet. Press FCT 72 and enter coefficient b from the pressure transducer calibration sheet. Press FCT 73 and set the Aux Channel Destination to 43. The mv reading from the pressure transducer found on the Aux channel is transformed by the calibration and will be displayed in kpa on channel 43. To view the pressure reading, press FCT 43, or set up a custom display and view barometric pressure along with one other channel of your choice. Note that the raw mv output of the pressure transducer is now measured at the Aux Input channel on the instrument back panel. Your data logger or recorder can be connected to the input channel, and the transformation can be performed on your own computer, if desired. The Aux Input is no longer available as an input channel. 15 Viewing geopotential height. This routine displays geopotential height (in feet or meters) based on the current value of pressure on channel 43. To view the geopotential height, press FCT 08 and select Geopotential from the list. The up and down arrows toggle the display between feet and meters. The height displayed is relative to sea level in a standard atmosphere. IRG3-071 LI-COR, inc Superior Street P.O. Box 4425 Lincoln, Nebraska USA Phone: FAX: Toll-free (U.S. & Canada)