Detcon PI-700 - Manual (Page 14)

Model PI-700
PI-700 Instruction Manual Rev. 2.5 Page 10 of 54
NOTE: If the 4-20mA output is not being used, a 100-250Ω resistor must be installed between
the mA and (-) terminals on the Transient Protection Module to ensure RS-485 communication
is not disrupted by a 4-20mA Fault.
a) If applicable, terminate the RS-485 serial wiring as shown in Figure 9. Use the second plug (Out) as
termination point on the customer side to facilitate a continuous RS-485 serial loop
The RS-485 (if applicable) requires 24 gauge, two conductor, shielded, twisted pair cable between the sensor
and host. General Cable Commodore part number ZO16P0022189 is recommended.
NOTE: Install a 120-ohm resistor across A & B terminals on the last sensor in the serial loop.
c) Trim all exposed wire leads if they are not permanently landed in the terminal block.
d) Replace the junction box cover.
2.7 Initial Start Up
Upon completion of all mechanical mounting and termination of all field wiring, apply system power in the
range of 11.5-30VDC (24VDC typical) and observe the following normal conditions:
a) PI-700 display reads close to “0”, and no fault messages are flashing.
b) A temporary upscale or downscale reading may occur as the sensor stabilizes. This upscale reading will
typically decrease to near “0”ppm within 1-2 minutes of power-up, assuming there is no gas in the area of
the sensor. In some extreme cases, the sensor may require up to 5 minutes before the lamp ignites and
becomes operational.
NOTE: The 4-20mA signal is held constant at 4mA for the first two minutes after power up.
Initial Operational Tests
After a warm up period of 1 hour (or when zero has stabilized), the sensor should be checked to verify
sensitivity to the specific target gas of the application (not just Isobutylene span gas).
NOTE: A secondary filter accessory, built into the splashguard adapter, is used with the Model
700 PID sensors (Figure 14). This multi-stage filter is designed to prevent heavy and complex
airborne VOC molecules from contacting the PID sensor and causing surface contamination
and subsequent reading drift. When used effectively, it may extend the time between required
sensor cleaning and / or sensor replacement. Its use is limited to application cases where the
target gas(s) are moderate to small VOC molecules (i.e. benzene and smaller molecular
weights). Before installing, it must be verified that the filter does not inhibit response to the
target gas being monitored. Do not use this filter if the target gas response is inhibited. The
service life of the filter may vary depending on the application; however, it is advised to
change it out at least on a 18-24 month cycle.
Material Requirements
 Detcon PN 613-120000-700 700 Series Splash Guard with integral Cal Port -OR-
 Detcon PN 943-000006-132 Threaded Calibration Adapter