ENMETENMET Corporation
PO Box 979
Ann Arbor, MI 48106-0979
TDX – Series
Explosionproof
Oxygen & Toxic Gas
Sensor/Transmitter
Operating Manual
80003-128
02-25-94
MCN-204; 06/24/99
MCN-219; 06/30/99
MCN-269, 02/08/02
Table of Contents
1.0 Introduction................................................................................................................................................................................................1
1.1 Unpack....................................................................................................................................................................................................1
1.2 Check Order...........................................................................................................................................................................................1
1.3 Serial Numbers......................................................................................................................................................................................1
2.0 Operation....................................................................................................................................................................................................2
3.0 Description of Components.....................................................................................................................................................................2
3.1 Description of Sensor...........................................................................................................................................................................2
3.2 Description of Transmitter...................................................................................................................................................................2
4.0 Installation of the TDX-Series Unit .......................................................................................................................................................3
5.0 Calibration of the TDX-Series Unit .......................................................................................................................................................4
5.1 Checking Channel Response to Gas..................................................................................................................................................4
5.2 Calibration of a Channel......................................................................................................................................................................5
5.2.1 Zero Point Adjustment.................................................................................................................................................................5
5.2.2 Span Calibration Adjustment......................................................................................................................................................5
5.2.3 Applying Calibration Gas ............................................................................................................................................................ 5
6.0 TDX Sensor Life and Replacement.......................................................................................................................................................6
7.0 Maintenance...............................................................................................................................................................................................6
8.0 Calibration Kits .........................................................................................................................................................................................6
9.0 WARRANTY .............................................................................................................................................................................................6
List of Illustrations
Figure 1: Sensor/Transmitter Module Diagram..........................................................................................................................................2
Figure 2a: Mounting Dimensions Diagram.................................................................................................................................................3
Figure 2: System Wiring Diagram................................................................................................................................................................3
Figure 3: Calibration Diagram.......................................................................................................................................................................4
TDX-Series ENMET Corporation
1.0 Introduction1.0 Introduction
The TDX-Series gas detection unit accurately monitors low concentrations of a designated toxic gas. An
electrochemical sensor design produces a linear response to low gas concentrations, providing accurate signal output
for recorder equipment interface.
NOTE: All specifications stated in this manual are subject to change without notice.
1.1 Unpack
Unpack the TDX-Series and examine it for shipping damage. If such damage is observed, notify both ENMET
customer service personnel and the commercial carrier involved immediately.
Regarding Damaged Shipments
NOTE: It is your responsibility to follow these instructions. If they are not followed, the carrier will
not honor any claims for damage.
q This shipment was carefully inspected, verified and properly packaged at our company and delivered to the
carrier in good condition.
q When it was picked up by the carrier at ENMET, it legally became your company’s property.
q If your shipment arrives damaged:
• Keep the items, packing material, and carton “As Is.” Within 5 days of receipt, notify the carrier’s local
office and request immediate inspection of the carton and the contents.
• After the inspection and after you have received written acknowledgment of the damage from the carrier,
contact ENMET Customer Service for return authorization and further instructions. Have your Purchase
Order and Sales Order numbers available.
q ENMET either repairs or replaces damaged equipment and invoices the carrier to the extent of the liability
coverage, usually $100.00. Repair or replacement charges above that value are your company’s responsibility.
q The shipping company may offer optional insurance coverage. ENMET only insures shipments with the
shipping company when asked to do so in writing by our customer. If you need your shipments insured, please
forward a written request to ENMET Customer Service.
Regarding Shortages
If there are any shortages or questions regarding this shipment, please notify ENMET Customer Service within 5 days
of receipt at the following address:
ENMET Corporation
680 Fairfield Court
Ann Arbor, MI 48108
734-761-1270 734-761-3220 Fax
1.2 Check Order
Check, the contents of the shipment against the purchase order. Verify that the TDX-Series is received as ordered. If
there are accessories on the order, ascertain that they are present. Check the contents of calibration kits. Notify
ENMET customer service personnel of any discrepancy immediately.
1.3 Serial Numbers
Each TDX-Series is serialized. These numbers are on tags on the equipment and are on record in an ENMET
database.
1
ENMET Corporation TDX-Series
Terminal
PCB
V+ (24VDC)
2.0 Operation2.0 Operation
TDX-Series Unit can be of single or multi-channel configuration. Each unit monitors the gas concentration at a single
remote location and consists of a sensor, transmitter. The sensor/transmitter without local read out can be connected to
a controller module via 2-conductor shield cable. The transmitter converts the direct output signal of the sensor into a
standard 4-20mA DC signal. The sensor/transmitter is mounted at a strategic location to monitor the designated
hazardous gas in ambient air.
3.0 Description of Components3.0 Description of Components
3.1 Description of Sensor
Sensor: The sensor consists of an electrochemical cell. As the designated gas passes through the cell
membrane, it reacts with the electrolyte to produce a small electrical current proportional to the
partial pressure of gas in the area.
3.2 Description of Transmitter
Cover Screws: These screws fasten the face cover to the transmitter unit. Face cover must be removed for
installation or for performing calibration adjustments.
Cable Entry: This fitting provides strain relief entry for cable from the controller module.
Zero Adjust screw: This screw is used to adjust the zero setting during calibration.
Span Adjust screw: This screw is used to adjust the sensitivity during calibration.
Terminal Strip: This terminal is used to connect the 24VDC power from a controller unit. (See installation for
proper wiring.)
Sensor
Span Adjust Screw
Zero Adjust Screw
TCX-Transmitter
Strip
Cable Entry
Figure 1: Sensor/Transmitter Module Diagram
V– (24VDC)
V+
V–
(PT–)
(PT+)
Multimeter Range:
40 to 200 mV
40mV = 4mA
200mV = 20mA
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TDX-Series ENMET Corporation
To Controller
2-conductor, 20 gauge (AWG)
4.0 Installation of the TDX-Series Unit4.0 Installation of the TDX-Series Unit
When determining locations for sensor/transmitter to a controller module, keep in mind the following:
• Maximum distance between sensor/transmitter and controller module is 3200 ft.
NOTE: Recommend transmission cable between transmitter and controller module to be AWG18 or equivalent, 2 core
shielded cable type. To accommodate a 4-20mA signal at 24VDC.
A wiring diagram for sensor/transmitter to controller module is shown in Figure 2.
A Dimensional Diagram is shown in Figure 2a.
After system is properly installed and power applied, allow 2 hours for warm up and stabilization, then proceed to
verify calibration.
3.03″
76.96
3.03″
76.96
Figure 2a: Mounting Dimensions Diagram
+ 24 VDC
– 24 VDC
shielded cable with drain wire
(for up to 2000 feet, 600 meters).
Figure 2: System Wiring Diagram
3
ENMET Corporation TDX-Series
TDX-Transmitter
TDX-Sensor
Calibration
Flexible
5.0 Calibration of the TDX-Series Unit5.0 Calibration of the TDX-Series Unit
5.1 Checking Channel Response to Gas
The TDX system is supplied precalibrated. After initial installation, the sensor should be checked with calibration/test
gas to confirm gas response. This test should be performed periodically (once every 3 – 4 months).
To check if the sensor requires calibration, introduce an appropriate calibration gas (gas of known concentration) to the
sensor. If there is a discrepancy of more than 10% between the voltage reading on the transmitter and the known
concentration of the gas, then the transmitter should be recalibrated.
Adapter
Tubing
Apply Calibration Gas
Figure 3: Calibration Diagram
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TDX-Series ENMET Corporation
5.2 Calibration of a Channel
5.2.1 Zero Point Adjustment
TOXIC ZERO POINT ADJUSTMENT:
Toxic Zero point adjustment is accomplished by exposing the sensor to clean, contaminant-free air for a few minutes.
The signal may be measured, by a standard millivoltmeter located between (PT+) and (PT-) as shown in Figure 1.
Adjust the ZERO ADJUST SCREW to accomplish this reading.
Toxic zero setting: At 0 ppm the signal should read 40mV = 4mA
OXYGEN ZERO POINT ADJUSTMENT:
It is normally not necessary to adjust the zero adjust screw for oxygen. This may be done to obtain optimum linearity
across the entire range (0 – 30% by vol.), if a new sensor is installed or the zero adjust screw has been accidentally
changed.
To set zero, it is necessary to expose the oxygen sensor to pure 100% nitrogen until a stable reading is obtained. This
can require flowing the nitrogen for 20 to 30 minutes.
Oxygen zero setting: The signal at 100% nitrogen/zero oxygen should read 40mV = 4mA.
5.2.2 Span Calibration Adjustment
A calibration gas is required for span adjustment. A calibration gas is either the same gas which the sensor is designed
to detect or a specified correlation gas. The calibration gas should be at a concentration close to the full scale
concentration of the transmitter range. Calibration gases may consist of gas cylinders, kit generated gases, permeation
tube-generated gases, etc.; any of these are acceptable, as long as the concentration of the gas is known and is close to
the transmitter full-scale concentration.
To perform the span adjustment, the calibration gas is introduced to the sensor at a low, constant flow rate (0.5 liters
per minute).
After 1-2 minutes, the SPAN ADJUST SCREW located inside the transmitter is adjusted so the signal measured
between (PT+) and (PT-) can be obtained by using the formula shown.
( ( ) + 4 ) x 10 = mV Across (PT)
Toxic Example: Calibrate a hydrogen sulfide transmitter to a range of 0 – 100 ppm using a calibration gas concentration of 100 ppm:
( ( ) + 4 ) x 10 = 200 mV Across (PT)
Oxygen Examples:
1. Calibrate an oxygen transmitter to a range of 0 – 30% B.V. using a calibration gas concentration of 19.5% B.V.:
( ( ) + 4 ) x 10 = 144 mV Across (PT)
2. Calibrate an oxygen transmitter to a range of 0 – 30% B.V. using clean fresh ambient air ,20.9 by volume: The
signal at 20.9% B.V. should read 151.5 mV = 15.1mA.
16 x (Gas Concentration)
Range of Sensor
16 x 100
100
16 x 19.5
30
5.2.3 Applying Calibration Gas
To apply calibration gas, carry out the following steps:
1. Apply the test gas of known concentration to the sensor using the calibration adapter provided (See Figure 3.).
2. Wait for a stable reading to be obtained. (1-2 minutes is a suitable period of time).
3. Adjust the SPAN ADJUST SCREW (See Figure 1) until the correct reading across (PT+) and (PT-) is shown.
4. Remove the calibration gas and adapter.
5. Calibration is now complete.
5
ENMET Corporation TDX-Series
6.0 TDX Sensor Life and Replacement6.0 TDX Sensor Life and Replacement
Gas sensors (three-electrode type) are designed for a minimum life span of 2 years. Oxygen sensors (two electrode
type) are designed for a life of 12 months. It is a question of customer policy whether the sensor is replaced
automatically after this time or when the sensor fails to calibrate.
7.0 Maintenance7.0 Maintenance
Maintenance consists of periodic calibration and sensor replacement when needed.
8.0 Calibration Kits8.0 Calibration Kits
ENMET offers calibration kits for all gases monitored.
9.0 WARRANTY9.0 WARRANTY
ENMET warrants new instruments to be free from defects in workmanship and material under normal use for a period
of one year from date of shipment from ENMET. The warranty covers both parts and labor excluding instrument
calibration and expendable parts such as calibration gas, filters, batteries, etc... Equipment believed to be defective
should be returned to ENMET within the warranty period (transportation prepaid) for inspection. If the evaluation by
ENMET confirms that the product is defective, it will be repaired or replaced at no charge, within the stated
limitations, and returned prepaid to any location in the United States by the most economical means, e.g. Surface
UPS/RPS. If an expedient means of transportation is requested during the warranty period, the customer is responsible
for the difference between the most economical means and the expedient mode. ENMET shall not be liable for any
loss or damage caused by the improper use of the product. The purchaser indemnifies and saves harmless the
company with respect to any loss or damages that may arise through the use by the purchaser or others of this
equipment.
This warranty is expressly given in lieu of all other warranties, either expressed or implied, including that of
merchantability, and all other obligations or liabilities of ENMET which may arise in connection with this equipment.
ENMET neither assumes nor authorizes any representative or other person to assume for it any obligation or liability
other than that which is set forth herein.
NOTE: When returning an instrument to the factory for service:
-- Be sure to include paperwork.
-- A purchase order, return address and telephone number will assist in the expedient repair and return of your
unit.
-- Include any specific instructions.
-- For warranty service, include date of purchase
-- If you require an estimate, please contact ENMET Corporation.
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