Omega TX787, TX788 User Manual

SPECIFICATIONS
Minimum Span
t/c: 20

0

C if zero offset < 6500C
500C if zero offset > 6500C
1250C if zero offset > 12500C

(type C only)

RTD: 120C if zero offset < 750C

200C if zero offset < 2750C
500C if zero offset > 2750C

mV: 1mV if zero offset < 25mV

5mV if zero offset < 150mV
10mV if zero offset > 150mV

mA: 1mA if zero offset < 15mA

3mA if zero offset > 15mA

Volts: 0.3V if zero offset < 5V

0.5V if zero offset > 5V

Input Impedence

Volts: 200kΩ
Millivolts: 10mΩ
Milliamps: 5Ω

t/c Burnout Function

Programmable: upscale or

downscale

t/c Burnout Detection Current

<0.2µA

RTD Excitation Current

0.3mA (nominal)

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Long Term Stability

Better than 0.1% of span in 12

months

Temperature Stability

<0.01% of span per

Isolation

1000VDC input to output

Minimum Output Current

3.85mA

Maximum Output Current

22.5mA

Loop Voltage Drop

< 9VDC at 20mA

Supply Voltage Range

9 - 36 VDC

Maximum Effect of Change in
Supply Voltage

<0.002% of span per Volt

Effect of Ambient Temperature
Change on Cold Junction
Compensation

0.020C/ 0C

CJC Accuracy

0.50C

Update Time

>3 Conversions per second

Turn On Time

< 4 Seconds

OMEGA ENGINEERING, INC. warrants this unit to be free of manufacturing defects for the life of the product.
If the unit should malfunction, it must be returned to the factory for evaluation. OMEGA's Customer Service Department will issue an
Authorized Return (AR) number immediately upon phone or written request. Upon examination by OMEGA, if the unit is found to be defective
it will be repaired or replaced at no charge. OMEGA's WARRANTY does not apply to defects resulting from any action of the purchaser,
including but not limited to mishandling, improper interfacing, operation outside of design limits, improper repair, or unauthorized modifica­tion. This WARRANTY is VOID if the unit shows evidence of having been tampered with or shows evidence of being damaged as a result
of excessive corrosion; or current, heat, moisture or vibration; improper specification; misapplication; misuse or other operating conditions
outside of OMEGA's control. Components which wear are not warranted, including but not limited to contact points, fuses, and triacs.

OMEGA is pleased to offer suggestions on the use of its various products. However, OMEGA neither assumes responsibility for
any omissions or errors nor assumes liability for any damages that result from the use of its products in accordance with
information provided by OMEGA, either verbal or written. OMEGA warrants only that the parts manufactured by it will be as
specified and free of defects. OMEGA MAKES NO OTHER WARRANTIES OR REPRESENTATIONS OF ANY KIND WHATSOEVER,
EXPRESSED OR IMPLIED, EXCEPT THAT OF TITLE, AND ALL IMPLIED WARRANTIES INCLUDING ANY WARRANTY OF MER­CHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE HEREBY DISCLAIMED. LIMITATION OF LIABILITY: The rem­edies of purchaser set forth herein are exclusive and the total liability of OMEGA with respect to this order, whether based on
contract, warranty, negligence, indemnification, strict liability or otherwise, shall not exceed the purchase price of the compo­nent upon which liability is based. In no event shall OMEGA be liable for consequential, incidental or special damages.

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CONDITIONS: Equipment sold by OMEGA is not intended to be used, nor shall it be used: (1) as a "Basic Component" under 10 CFR 21

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in or with any nuclear installation or activity, medical application, used on humans, or misused in any way, OMEGA assumes no responsi­bility as set forth in our basic WARRANTY/DISCLAIMER language, and additionally, purchaser will indemnify OMEGA and hold OMEGA
harmless from any liability or damage whatsoever arising out of the use of the Product(s) in such a manner.

Direct all warranty and repair requests/inquiries to the OMEGA Customer Service Department. BEFORE RETURNING ANY PRODUCT(S) TO OMEGA,
PURCHASER MUST OBTAIN AN AUTHORIZED RETURN (AR) NUMBER FROM OMEGA'S CUSTOMER SERVICE DEPARTMENT (IN ORDER
TO AVOID PROCESSING DELAYS). The assigned AR number should then be marked on the outside of the return package and on any correspondence.
The purchaser is responsible for shipping charges, freight, insurance and proper packaging to prevent breakage in transit.

FOR WARRANTY RETURNS, please have the following information
available BEFORE contacting OMEGA:

1. P.O. number under which the product was PURCHASED,

2. Model and serial number of the product under warranty, and

3. Repair instructions and/or specific problems relative to the product

OMEGA's policy is to make running changes, not model changes, whenever an improvement is possible. This affords our customers the latest in technology
and engineering.
OMEGA is a registered trademark of OMEGA ENGINEERING, INC.
ã Copyright 1996 OMEGA ENGINEERING, INC. All rights reserved. This documentation may not be copied, photocopied, reproduced, translated, or reduced
to any electronic medium or machine-readable form, in whole or in part, without prior written consent of OMEGA ENGINEERING, INC.

It is the policy of OMEGA to comply with all worldwide safety and EMC/EMI regulations that apply. OMEGA is constantly pursuing certification of its products to
the European New Approach Directives. OMEGA will add the CE mark to every appropriate device upon certification.
The information contained in this document is believed to be correct but OMEGA Engineering, Inc. accepts no liability for any errors it contains, and reserves the
right to alter specifications without notice.
WARNING: These product are not designed for use in, and should not be used for, patient connected applications.

Filter Band

Programmable from 0 to 120%

Damping

Programmable from 0.0 to 32.0

0

C

seconds

Common Mode Rejection

120dB

Operating Temperature Range

-20 to 70oC

Dimensions mm(inches)

H 55.3 (2.10) X W 77.7 (3.06)
X D 61.0 (2.40)

Weight

0.56lbs

Warranty

3 years

WARRANTY/DISCLAIMER

RETURN REQUEST/ INQUIRIES

FOR NON-WARRANTY REPAIRS, consult OMEGA for current
repair charges. Have the following information available BEFORE
contacting OMEGA:

1. P.O. number to cover the COST of the repair,

2. Model and serial number of product, and

3. Repair instructions and/or specific problems relative to the
product.

721-0709-00A 8/98

TX787, TX788
Programmable, Isolating T wo-Wire Temperature T ransmitters

Instruction Sheet M-2919

APPLICATION

Model TX787 and TX788 is an ex­tremely versatile two-wire transmit­ter that may be used in any applica­tion requiring an isolated 4-20mA
current loop proportional to a ther­mocouple, RTD, millivolt, milliamp,
voltage, resistance or potentiometer
input. Typical applications include
providing accurate, stable signals to
distributed control systems (DCS),
supervisory control and data acqui­sition systems (SCADA), environ­mental monitoring and control sys­tems (EMCS), data acquisition and
control systems (DACS) and cus­tody transfer / pipeline systems. The
output of the TX787 and TX788 may
also be used by an analog or digital
display device.

DESCRIPTION

The TX787 is a programmable two­wire transmitter that is configured to
provide an isolated 4-20mA signal in
proportion to the desired range of its
input signal. The TX787 accepts ther­mocouple, 2-,3-, or 4 wire RTD, po­tentiometer, and millivolt inputs. The
TX788 accepts millivolt, voltage, and
milliamp inputs.

Configuration is performed by con­necting the transmitter to a standard
PC serial port (9-pin RS232C) using
an isolated interface adapter and
running a user-friendly, Windows­based program. Unique
technology in the TX787 allows all
configuration information to be de­fined and modified with only a PC,
the interface adapter, and the trans­mitter. No loop supply, input simula­tion, or meter on the output is re­quired! The fully isolated adapter
reduces the risk of expensive dam­age to the PC which can be caused

PC-Only

by spikes and surges on field wiring
entering the computer via its unpro­tected serial port.

The TX787 utilize state of the art
microprocessor technology and
yields higher accuracy and long­term stability with lower power con­sumption than prior generation trans­mitters. The device automatically
performs frequent self-testing and
auto-calibration while in service, re­sulting in very stable long-term per­formance - stability greater than

0.1% of span over 12 months.
To maximize traceability, each unit

may be assigned a tagID, a job or a
project number, the purchase order
and date on which it was procured,
and a message in addition to its
serial number. This data, along with
the selected input type and range,
last calibration date, and serial num­ber are stored in the transmitter.

OPERATION

Every TX788 is factory calibrated
and may be simply configured to
perform the desired function using
the Device Configuration screen (fig­ure 1) and the Sensor Selection
screen (figure 2) shown. Just fasten
the DB-9 connector to the computer's
serial port and the keyed 5-pin con­nector to the port under the access
cover on the top or the transmitter.
There is no need to provide an ex­ternal power supply and load to the
TX787's output to configure the
transmitter.

Units previously placed in service
may have their configuration " up­loaded" to the PC. Their operating
parameters may be reviewed and if
necessary revised and downloaded
again. All configuration parameters

may be stored in a "configuration
file" on the PC for future use.

After configuration, and at periodic
intervals, the calibration may be veri­fied by simulating and varying the
input signal over the defined range
and comparing the output signal to
the ideal. If calibration is necessary,
the PC software is used to adjust the
transmitter's digital references. Be­cause of the self-calibrating technol­ogy utilized in the TX787, the cali­bration verification interval may be
significantly longer than for earlier
technology transmitters.

The Calibration and Configuration
Software, Isolated RS232/TX787
Communications Adapter and User's
Guide are included in the model
TX780-SOFT.

INPUT CONNECTIONS

Figure 1

Device Configuration

Figure 2

Sensor Selection

Table 2

(1) Accuracy includes input accuracy, output accuracy, and
linearity for any 2500C span within the conformance range at a
stable 250C ambient temperature; minimum accuracy over entire
conformance range is + 0.1% of full conformance span.

(2) For other RTD Types, consult Factory

TX787

TX788

FIELD MOUNTING

The TX787 is designed for installation in
industrial field environments. A sealed,
die-cast aluminum housing protects
against corrosion, moisture, dust and
electrical noise such as radio frequency
(RFI) and electromagnetic (EMI) inter­ference. All circuit boards are urethane
coated for environmental protection.

Table 1

(3) α =.00385 and .003916
(4) Percent of full scale range