Sensata SC420TWHL Series 420 Family of Isolating Signal Conditioners User Manual
- June 3, 2024
- Sensata
Table of Contents
Sensata SC420TWHL Series 420 Family of Isolating Signal Conditioners
Whilst every effort has been taken to ensure the accuracy of this document, we accept no responsibility for damage, injury, loss or expense resulting from errors or omissions, and reserve the right of amendment without notice. This document is issued by Sensata Technologies and may not be reproduced in any way without the prior written permission of the company
INTRODUCTION
The SC420TWHL series is a family of isolated two wire 4 – 20 mA transmitters
capable of accepting a variety of electrical input types and operating with an
output loop voltage of 12 to 32 V DC.
The input signal is the only parameter required to define any unit exactly.
This information, together with a unique serial number, is printed on the side
label of each unit; records of the exact configuration of every product
shipped are maintained at the factory.
Input Types and Ranges
SC420TWHL – HL (Previously designated SC420TWHL – 0 / SC420TWHL – 1) Accepts
either voltage or current (i.e. high level) inputs. The standard default
configuration of the unit allows 4 – 20 mA, 0 – 20 mA, 2 – 10 V or 0 – 10 V
inputs to be reconfigured by the user. However a much wider range of inputs is
available to order. In general the limits on signals that can be handled with
the accuracy specified in Section 7 are:
Standard process ranges such as 0 – 5 V or 1 – 5 V are of course covered.
SC420TWHL – TC (Previously designated 420 TW – 2)
Accepts inputs directly from the following thermocouple types:
E,T,K,T,N,R,S,F. Temperature ranges from 0 – 100 oC to 0 – 2000 oC can be
reconfigured (mV outputs without cold junction compensation can be catered for
to special order). All specified ranges are 0 oC referred, although negative
inputs will not damage the unit. Automatic cold junction compensation is
provided. Either upscale or downscale output drive, on sensor wire break
detection, can be selected. The output is not linearized. Although any
thermocouple type can be selected for any temperature range, the table below
indicates the ranges for which the accuracy specified in section 7 is
achieved:
UNPACKING
Please inspect the instrument carefully for signs of shipping damage. The unit is packaged to give maximum protection but we can not guarantee that undue mishandling will not have damaged the instrument. In the case of this unlikely event, please contact your supplier immediately and retain the packaging for our subsequent inspection.
Checking the Unit Type
Each unit has a unique serial number label (fig.1 below) on which full details
of the configuration are given. These details should be checked to ensure
conformance with your requirement.
CONNECTIONS
Before proceeding, please check the information on the serial number label on one side of the unit to ensure that the unit configuration is correct (see Fig. 1 above). Connection details are given on the front panel label of the unit, adjacent to the relevant connections (see Fig. 2 above).
Loop Supply Voltage
The voltage across the output loop terminals must not exceed 32V DC –
otherwise damage to the instrument may result. The unit is protected against
reverse polarity connection.
RECONFIGURING THE INSTRUMENT (applies to reconfigurable units only)
In many cases the instrument will have been factory configured to the required specifications, and calibrated, in which case this section can be ignored. If a particular configuration is not specified then the default (specified below) will be supplied.
Input Configuration
This section details the steps required to reconfigure the unit, after which
recalibration will be necessary.
SC420TWHL
Current or voltage input can be selected to achieve any of the following DC
inputs:
- 0-20mA
- 4-20mA
- 0-10V
- 2-10V
(If the input is not specified at the time of order the default configuration of 4 – 20 mA will be set).
To reconfigure the instrument remove the side cover without the serial number label from the unit – this cover is a push fit and can be prised off with a thumb nail or small screwdriver. The three links B1,B2,B3, should be open or short circuit according to the following table:
WARNING : TAKE GREAT CARE NOT TO DAMAGE THE DELICATE COMPONENTS ADJACENT TO THE LINKS.
After reconfiguration replace the side cover
420 TW-TC
Thermocouple type, range and wire break detect action are all user
reconfigurable. (If the input is not specified at the time of order the
default configuration of type K, 0 – 100oC, up scale will be set).
S1 – Thermocouple Type
NB. Only Switch Position ‘0’ Is Marked.
S2 – Range (0°-Full Scale)
N.B. Only Switch Position ‘0’ Is Marked. Rotate Clockwise To Increment Position
(Diagram above shown in position 6) S3 – Burnout
To reconfigure the instrument remove the side cover without the serial number label from the unit – this cover is a push fit and can be pushed off with a thumb nail or small screwdriver. Set the three switches S1, S2, S3 to the desired positions and replace the side cover.
RECALIBRATION
All units are factory calibrated; although the user may wish to recalibrate with greater frequency, a two yearly recalibration interval is adequate for most applications. In the case of reconfigurable units, recalibration must be carried out after any change of configuration
SC420TWHL
With appropriate input values use front panel zero and span pots to obtain
desired zero scale and full scale voltage or current output (preferably with
the actual circuit loop voltage and load resistance, for greatest accuracy).
It may be necessary to repeat each adjustment to ensure correct calibration.
420 TW-TC
To recalibrate the unit a thermocouple simulator, (or for critical
applications a millivolt source and ice-point reference) 24V DC power supply
and accurate milliammeter/DMM are required
- Connect the equipment as shown in figure 5.
Note that if a T/C simulator with automatic internal cold junction compensation is used, thermal equilibrium between the simulator and the 420 TW-TC must be established. In any case the compensation applied to the simulator must be equal to the 420 TW-TC input terminal temperature
- Referring to Figure 6, if configuration has been changed coarse range potentiometer, CS, must first be adjusted (to access VR1, remove the side cover with serial number label).
- Set input to full scale
- Turn span potentiometer fully anti-clockwise to obtain minimum output current. Then adjust 6 turns clockwise
- Adjust CS to give nominal 20mA output (19mA
- Set input to zero and adjust zero potentionmeter (marked Z on circuit board) to give 4mA
- Set input to full scale and adjust span potentionmeter (marked S on circuit board) to give 20mA
- Repeat (i) and (ii) as necessary
INSTALLATION
Installation onto Rails
The instrument is designed to mount directly onto either the “Top hat” TS35
standard assembly rail to DIN 46277 part 3/EN 50022/BS5584, or the
asymmetrical 32 mm G-rail to DIN 46277 part 1/EN50035/BS5825.
Mounting Arrangements
Ideally the unit should be mounted in a vertical position, i.e. on a
horizontal rail. This is the optimum orientation to minimize temperature rise
within the unit. However successful operation is possible in any orientation.
Ensure the maximum ambient temperature is less than 70°C. Good airflow around
the unit will maximize reliability.
Wiring Precautions
The unit can accept a variety of sensor inputs, some of which produce very
small signals. Therefore it is advisable to adhere to the following rules of
good installation practice
- Do not install close to switchgear, electromagnetic starters, contactors, power units or motors.
- Do not have power or control wiring in the same loom as sensor wires.
- Use screened cable for sensor wiring with the screen earthed at one end only.
- Take care not to allow cut pieces of wire to fall onto the unit as they might enter via the ventilation holes and cause electrical short circuits. if in doubt, remove the units from the rail until wiring is complete.
- Use bootlace ferrules on all bare wires.
IMPORTANT : The connection terminals are designed for a maximum torque of 0.4Nm. Exceeding this figure is unnecessary and will result in unwarrantable damage to the unit.
SPECIFICATIONS
All specifications are at 20C operating ambient with 250 output load and 24V loop voltage unless otherwise stated.
Accuracy and Response
SC420TWHL
- Calibration accuracy at zero and full scale +/- 0.05% full scale
- Linearity +/- 0.1% full scale
- Zero drift + / – 50ppm full scale /C
- Gain drift +/- 100ppm /C
- Gain dependence on load resistance, RL +/-5ppm / 0 RL 600
- Response Time (90% of step change) 30ms typical
- Output loop voltage range (RL=O) 10 to 32V DC
- Max Input Voltage drop (20mA input) 0.3V
- Input impedance (0 – 10 V input) 1M
420 TW-TC
- Calibration accuracy at zero and full scale +/- 0.2 full scale
- Cold junction compensation accuracy +/- 2 °C over operating temperature range
- Linearity (with respect to thermocouple voltage) +/- 0.1 % full scale
- Zero Drift +/- 50ppm full scale /°C
- Gain Drift +/- 100ppm /°C
- Gain dependence on load resistance, RL +/-5ppm /,0 RL 600
- Response time (90% of step change) 300ms typical (higher speed version available)
- Output loop voltage range (RL=O) 11 to 32 V DC
- Sensor break detect current +/- 250nA
Power Supply Isolation and Operating Ambient (all types)
- Operating Voltage 11 – 32 V DC
- Current 29 mA maximum overscale
- Input to output isolation 1kV DC
- Operating temperature range -15 – 70C
- Storage temperature range -40 – 100C
- Operating and storage humidity range 0 – 90% RH
EMC performance
- EMC BS EN61326
- LVD Standards EN61010-1
- Installation Category (IEC 664) II
- Pollution Degree (EN61010-1) 2
- Equipment Class (IEC 536) II
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