REMOTE INTELLIGENT SENSOR - AREA MONITOR
4.8MEASURING PUMP CURRENT
To establish the pump run current, first check the system current in the TEST Mode. Then the total current is measured as detailed below and the TEST Mode current deducted from total current to give pump current. If the printer option is fitted, the total current is shown on the printout header. If it is not, total current can be measured with a suitable multimeter in series with the RIS 12 VDC input at J1 terminal #2.
When the meter has been connected, switch the RIS on and take a reading during the normal sampling period. This starts immediately after the purge cycle. Do not measure the current during the purge cycle because the pump is running at a higher than normal rate.
It is not necessary to check the pump run current frequently but an excessive current is a good indication that a pump requires attention, or replacing. The following ‘normal’ range of pump current is provided for guidance.
Low Flow Pump, RIS systems with a flow rate of 250 mL/min. or less: ‘typical’ current range = 90 to 120 mA. A pump current of 200 mA or more indicates a faulty pump that requires replacement.
High Flow Pump, RIS systems with a flow rate of 700 mL/min. or more: ‘typical’ current range = 250 to 300 mA. A pump current of 400 mA or more indicates a faulty pump that requires replacement.
4.9RESETTING THE PRINTER OPTION STORAGE
The stored data can be cleared any time. Enter the TEST Mode, press the HOLD/RELEASE key at any point in the cycle, and then press the PRINT key. Exit the TEST Mode to return to normal operation. Storage resetting can be verified by initiating a printout. The header will show ‘printout CANCELED’ in acknowledgment.
4.10CLEANING THE SAMPLING INPUT AND OPTICS BLOCK
4.10.1INTRODUCTION. The RIS draws the atmosphere to be monitored through the optics block. This assembly conveys the sample to the tape and houses the LED’s (light emitting diodes), and photodiodes. These devices, respectively, initiate and receive the beam of light that is bounced off the tape and used to determine the sample concentra- tion by measuring the stain density.
If the sample drawn through the optics block contains dust, other airborne particles or aerosols,
these substances will, in time, tend to coat the optic elements mentioned above. In addition, they may accumulate in the input tube and the air path through the optics block.
The effect of this process is to gradually degrade the performance of the optics block. This deteriora- tion can progress to the point where the light level adjustment is no longer able to compensate. When this occurs, remedial action is necessary. The following information provides guidance on light level adjustment and cleaning procedures.
4.10.2LIGHT LEVEL ADJUSTMENT. The acceptable light level range, (checked in the TEST Mode), is between 200 and 254 and applies to both tracks. Recommended practice is to check the levels at each cassette change and adjust to 220 on the tape being used. The 220 value allows for small naturally occurring changes in level, without the extremes of 200 or 254 being reached. The ad- justment procedure is provided in Section 4.4.
4.10.3WHEN TO CLEAN. Unless conditions are adverse, it is unusual for the air paths to need cleaning more frequently than every 9 to 12 months.
Be guided by experience and adjust cleaning frequency accordingly.
An exception to the norm is where there are significant sticky aerosols present in the monitored atmospheres. This situation can occur when MDI is sampled. In such cases careful regular cleaning of the input tube, and the air path through the block, may reduce the need for more extensive cleaning. An indicator that cleaning is required is an inability to restore the light levels to the 220 value
by means of the adjustment provided.
4.10.4HOW TO CLEAN. To clean the input tube, unscrew the external clamping nut and the input assembly parts can be withdrawn. The actual sample tube can be easily gripped and removed if a short piece of a larger diameter silicone rubber tubing is put over it.
When it has been removed, clean the input tube with a cotton tipped swab (or similar) and, if re- quired, use a residue free solvent spray.
NOTE: RIS’s with two input tubes (e.g.. MDI systems) have different parts but the method of disassembly is similar.
To clean the air passage in the block, put a piece of tape into the gate (tape from an old cassette can be used) and close it. Blow into the sampling port side of the block (after the input tube has been removed) to shift dust and loose debris. Then, open the gate and move a clean piece of tape into position.
Instruction | Page |
