PEMTECH PT395 Series User manual

Model PT395
Stand Alone Sensor
For Combustible Hydrocarbons
Revision 6
Operator’s
Manual
Pem-Tech, Inc.
Houston, Texas
U.S.A

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Table of Contents
Notice and limited Warranty 3
Service Policy 4
Specifications 6
Overview 7
Target gases and Detection Ranges 8
Transmitter Board assembly 9
Connection Board assembly 10
Wiring Diagram
DC Power and 4-20mA Signal Output 11
Low and High Alarms 12
Installation 13
Start Up 15
Normal Operation 16
Gas Reading Display 16
Signal Output 4-20mA 16
Alarm Conditions 17
Low & High Alarm, Fault 17
Resetting Alarms 18
Calibration 19
Sensor calibration 19
Recommended Calibration Gases 21
Calibration errors and remedies 22
Calibration Flow Chart 23
Description, General Information 24
Selective response to different Combustible Gases
Adjust alarm set points 26
Setting Low & High Alarm Levels 26
MAINTENANCE
Factors affecting sensor accuracy 28
Routine maintenance 28
Sensor Inspection 28
Sensor Sensitivity 28
Sensor Replacement 29
Spare Parts 30

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NOTICE
PEM-TECH INCORPORATED SHALL NOT BE LIABLE FOR TECHNICAL OR
EDITORIAL ERRORS OR OMISSIONS MADE HEREIN; NOR FOR INCIDENTAL
OR CONSEQUENTIAL DAMAGES RESULTING FROM THE FURNISHING,
PERFORMANCE, OR USE OF THIS MATERIAL.
LIMITED WARRANTY
PEM-TECH Incorporated warrants all equipment manufactured by it to be free from
defects in workmanship and material, provided that such equipment was properly
selected for the service intended, properly installed, and not misused. Equipment
received by Pem-Tech for warranty repair or replacement will be return-shipped at
the lowest transportation cost.
The warranty provided by Pem-Tech does not cover defects which result from acts
beyond the control of PEM-TECH including, but not limited to: damage by accident,
negligence, tampering, or failure to operate in accordance with the procedures
outlined in the Operations Manual. PEM-TECH’s liability under no circumstances
will exceed replacement of the unit claimed to be defective.
The warranties specified herein are in lieu of any and all other warranties, express or
implied. In no event, whether as a result of breach of warranty or alleged
negligence, shall PEM-TECH be liable for special or consequential damages,
including, but not limited to, loss of profits or revenue; loss of equipment or any
associated equipment; cost of capital; cost of substitute equipment, facilities or
services; down time costs; or claims of customers of the purchaser for such damages.
Please call factory for RMA (return merchandise authorization) number before sending any
equipment for repair or replacement.

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SERVICE POLICY
Pem-Tech has service facility at the factory. For all the repairs contact at our toll free
number 1-800-379-3894 or visit our website www.pem-tech.com
For all repairs call us for a Return Material Authorization number (RMA). Inform us
briefly the nature of the problem and obtain shipping address. Properly pack the
equipment before shipping. Also include your complete shipping address and
contact name and phone number.
For non-warranty repairs you must provide the limit to repair costs. State if a quote
for repair cost is required before you can authorize the repair cost. For this an
additional charge may be applicable.
NOTE:
1. For all the repairs under warranty, serial number must be legible on the items
being repaired.
2. Shipping point is FOB Houston.

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IMPORTANT
Be sure to read and understand this instruction manual before installing, operating
or servicing the gas detection equipment.
WARNING
Do not open the sensor enclosure with power applied unless it is verified that no
combustible gases or vapors are present. Calibration or maintenance should not
be performed if there is any indication of the presence of combustible gas near
the sensor.
If anytime an intrusive sensor calibration procedure has to be performed then de-
classify the area before opening the sensor junction box.
The sintered flame arrestor on the stainless steel sensor head is an integral part of
the complete sensor assembly. Do not operate the gas sensor with the flame
arrestor removed or damaged.
CAUTION
If needed the sensor threads should be coated with silicone free grease. The
junction box cover threads should also be lubricated .
Silicone based lubricants must never be used.
Follow the wiring instruction for proper and safe operation under normal
conditions. Be sure that all wiring complies with NEC and all local ordinances.

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SPECIFICATIONS
SENSOR TYPE Catalytic Beads
WEIGHT 4 Lbs.
RANGE 0 –100 % LEL
TEMPERATURE RANGE: -40 F to 158 F ( -40 C to 70 C )
HUMIDITY: 0 to 95% RH, non-condensing
ACCURACY: 5 % of full scale
REPEATABILITY: 5 % of gas applied
RESPONSE TIME: With 100% LEL gas applied:
50% full scale in < 10 seconds
90% full scale in < 30 seconds
( CSA Performance Test )
CLASSIFICATION: CSA Class I, Div. 1 Groups B,C, & D
C22.2 No 152
CE0081 II 2 G Ex d IIC T6
Suitable for use in hazardous locations
POWER INPUT: 14 - 30 VDC ( 24VDC Nominal)
POWER CONSUMPTION: < 4 Watts
ANALOG OUTPUT 4-20mA DC linear.
Maximum of 300 Ohms loop resistance
DISPLAY 3 Digit LED display.
ALARM RELAYS Low, High, & Malfunction Relay contacts
Normally open or Normally closed,
Form “C” type. Relay rating: 1 amps @ 30VDC
VISUAL ALARM Alarm LED indicators
INDICATORS Amber for Low alarm,
Red for High alarm &
Red for Malfunction

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Overview
Model PT395 is a single point fixed sensor for the detection combustible
hydrocarbon vapors in ambient air. Detection range is 0 –100 % LEL (Lower
Explosive Limit). PT395 displays the gas concentration and transmits a linear 4-
20mA analog output signal that is proportional to the gas concentration displayed.
The unit is also equipped with 3 forms “C” type alarm relay contacts. Two (2) alarm
relays are fully programmable as Low and High alarms and 1 for sensor Fault or
Malfunction.
The sensor also features a non-intrusive calibration. Calibration is performed by
activating an internal magnetic switch. All calibration and alarm configuration data
is maintained in a non-volatile memory
Sensor transmitter board and connection board are enclosed in an explosion proof
junction box (rated Class I, Div 1 & 2). The unit consists of three assemblies, the
transmitter and display board, the connection board, and the stainless steel sensor
head assembly. Each of these assemblies can be purchased separately.
Figure 1. Model PT395 Sensor

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Transmitter Board
The transmitter board assembly consists of the signal conditioning circuit,
microprocessor, digital display and 4-20 mA output circuit. Three (3) LED provides
visual indication of currently active alarms. The transmitter board assembly is
connected to the connection board via ribbon cable and secured onto the stand-off
via two thumb screws. To remove the transmitter board simply move the thumb
screws counter-clockwise and slowly pull the transmitter board away. Unplug the
ribbon cable to completely remove the transmitter board from sensor unit.
Note: Do not use force to tighten the thumb screws when installing the transmitter board
back on the connection / termination board.
Figure 2. Model PT395 Transmitter and connection board assembly
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Connection Board
The termination or connection board consists of relays and DC-DC power converters
for the transmitter board and the sensor. The power converters are protected
against reverse polarity.
A 3 pin terminal is provided for user interface to the monitoring device for power
input and 4-20ma output. Three (3) Pin terminal blocks are also used for alarm
connections. Each pin on alarm terminal block is as C (common), NC (normally
closed) and NO (normally open). See Figure 3.
The 3 pin terminal at the bottom of the board is labeled SENSOR. Three (3) wires
from the sensor head assembly are connected to this terminal.
These wires are connected as follows:
R Red wire (Sensor Positive 2 VDC Supply)
B Black Wire (Sensor Ground)
G White Wire (Sensor signal out)
For proper operation these wires must be connected as noted above.

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Wiring Diagram: DC Power and 4-20mA signal output
Figure 3. Connection to DC Power Supply and PLC input module
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Wiring Diagram: Low and High Alarms
Figure 4. Connection to Alarm warning devices
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Installation
Refer to figure 5 for model PT395 explosion proof enclosure for mounting and
conduit connection.
Figure 5. Explosion proof sensor enclosure.
Follow steps below for installation.
1. Remove the enclosure cover and un-plug the transmitter board by simply
moving the thumb screws in counter-clockwise direction until they have loosen
up. Slowly pull the transmitter board and detach the ribbon cable. Do not
completely un-screw or remove the thumb screws from the transmitter board.
2. Mount the enclosure. Refer to the figure above for mounting hole dimensions.
Avoid mounting the sensor to fixtures with heavy vibrations.
3. Using a 3 conductor cable connect the termination board with the monitor or
controller as shown in figure 3. For the cable size a reference table is provided
below.

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4. Connect the transmitter board with the connection board with the 10 pin ribbon
cable. Mount the transmitter board on two 2 stand-offs using thumb screws on
the board. Note: Do not apply excessive force to tighten the screws.
5. Place the cover back on the enclosure.
Reference Wire size Table
Wire Size
Max Distance / Wire length
14 AWG
3300 Feet
18 AWG
1400 Feet
16 AWG
2200 Feet
20 AWG
900 Feet
Note: The table above is for reference only

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Start Up
After installation apply power to the unit. Allow the sensor to warm up for at least
15 minutes. For Ammonia sensors allow at least 2 hours for warm up time. Upon
power up the unit will display 00 on the LED display. After a few moments the
low alarm LED will light up and the digital display will show the low alarm set
point for about 8 to 10 seconds. The low alarm LED will then go off and high alarm
LED will light up with the digital display showing the current high alarm set point.
After few seconds the sensor will return to its normal operation. If different alarm
set points are desired then refer to section “Adjust Alarm Set Points” to modify
alarm parameters.
If the sensor does not start with the sequence as stated above or 00 is not displayed
check to see if the ribbon cable connector is properly inserted. If necessary unplug
the ribbon cable and plug it back again. The connector is keyed and can be inserted
only one way.
The sensors are calibrated at the factory before they are shipped. However, it is a
good practice to check the accuracy by simply applying the calibration gas after the
warm up time and check to see if the concentration displayed is as desired. If
calibration is required then follow the steps in the Calibration procedure.

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Operation
Normal Operation
The sensor is considered in normal operation after startup procedure is complete
and is not indicating any alarm or sensor fail (FAULT) condition.
Gas Reading Display
The sensor displays the gas concentration in % volume. Detection Range is 0 -100
% LEL
Signal Output 4-20mA
The 4-20mA signal output is directly proportional to the detection range of the
sensor. The output signal generated is proportional to the gas concentration
displayed on the LED display of the unit.
Use the formula below to compute the mA output for any given gas concentration
or vice versa.
Formula to convert gas reading to mA:
( 16 x gas_reading ) + 4 = Analog output (mA)
Detection Range
Formula to convert mA to gas reading:
( mA Output - 4 ) x Detection Range = gas_reading
16
(Note: Detection Range is the full scale range of the sensor)

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Alarm Conditions
Low Alarm
When the gas concentration displayed reaches the predefined alarm set point then
the low alarm condition exists. The low alarm (yellow) LED indicator will light up
and low alarm relay is energized.
High Alarm
The sensor is said to be in high alarm condition if the gas concentration reaches the
high alarm set point. The high alarm (red) LED indicator lights up and the high
alarm relay is energized.
Fault (Sensor Fail)
PT395 is in Fault (Malfunction) condition when the sensor assembly malfunctions.
In Fault condition the 4-20mA output generated would be less than 1.0 mA.

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Resetting Alarms
If any alarm is set as Non-Latching then the alarm condition clears once the gas
concentration falls below the pre set alarm level.
If the Latching option is selected then the alarm must be manually reset. To do this
place the magnetic tool against the cover. The magnetic sensor is located at the 4
o’clock position. Continue to hold the magnet to the cover and the sensor will
display “rSt” (short for RESET) on the LED display for few seconds.
Figure 6. Magnetic Sensor Position 4 o’clock to RESET alarms and
to adjust alarm levels / set points.

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Calibration
Refer to Table at the end of this section for the recommended calibration gas for the
target sensor. Also see section on Spare Parts for part numbers for other calibration
accessories.
Following items are needed for the sensor calibration:
Calibration adapter with tubing
Magnet tool to activate the magnetic sensor on the transmitter board assembly.
Calibration gas bottle with flow regulator. The flow of the calibration gas
should be approximately 1.5 LPM (liters per minute)
See Figure 8
Model PT395 sensor can be auto calibrated without removing the enclosure cover
and declassifying the zone. A magnet tool is used to activate the internal switch to
initiate the calibration. Once the calibration is initiated the alarm relay will be
deactivated and the 4-20mA analog signal will be held at approximately 2mA to
avoid any false alarm.
Follow the steps below to calibrate the sensor.
1. Make sure there are no combustible vapors present in ambient air.
2. Remove the rain / splash guard if attached.
3. Place the magnetic tool against the cover at 8 o’clock position to activate the
magnetic switch as shown in figure 7
3. Place and hold the magnet until LED display on the front panel starts flashing
CAL. Move the magnet away from the cover.
4. While the display is flashing CAL the sensor is making its initial adjustments. It
may take 5 to 10 seconds. (Note: Do not apply calibration gas yet)
5. Once the initial adjustments are made the sensor will display and flash 50,
meaning 50% LEL Calibration gas.

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6. The microprocessor waits 60 seconds for the user to apply the calibration gas
while flashing the display approximately twice every second. Attach the
calibration adapter to the sensor head assembly and turn the gas on. When the
flow of the gas is detected by the sensor the display flashing rate will slow down
to once every second. If no gas is detected within 60 seconds the sensor aborts
calibration and will display E-3 error code “Calibration Time Out” for few
seconds before returning to normal operation..
7. Apply the calibration gas for about one and a half (1 ½) minute.
8. After minute and a half the sensor will display Adj for 5 to 15 seconds while
making adjustments and recording the calibration data into memory. When
completed the display will starts flashing rapidly. At this time remove the
calibration gas and allow the sensor to clear. Do not remove the calibration
gas while Adj is being displayed. Remove the gas only when the adjustment is
completed and the display is rapidly flashing with calibration gas value.
9. The sensor calibration has been successfully completed
10. While the gas from the sensor housing is being cleared the 4-20mA analog output
will be held at 2.0mA and alarm relay will not be activated until the sensor has
cleared. Once cleared the unit will return to its normal operation. The 2mA level
on the analog output line is an indication to any connected gas monitor that the
sensor is in calibration mode thus avoiding any false alarm.
Also refer to “Sensor calibration Flow Chart” for quick calibration review and
“Calibration Error and remedies”
Figure 7. Magnetic switch position to activate Calibrate Mode

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Figure 8. Sensor Calibration using flow regulator and calibration
adapter.