Wiring and installation recommendations for the model TBX AES 400
(Original Document)
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Wiring recommendations
To protect the signal from induced external noise in serial mode and noise in common mode, it is advisable to take the following precautions regarding:
Precautions to take
Type of conductors
Use screened twisted pairs, with a minimum conductor cross-section of 0.28 mm2.
Cable screening
Connect the cable screening to the shortest TBX module ground on the TBX GND 015 grounding strip.
Arrangement of the conductors in cables
Multipair cables can be rearranged for signals of a similar type which have the same reference to ground.
Cable routing
Keep the measurement wires separate from the discrete I/O cables (in particular from relay outputs) and from power cables.
Sensor reference to ground
The TBX AES 400 has 4 inputs which are isolated from the PLC bus and from each other.
This double isolation means that sensors of different voltages can be used.
For safety reasons, a grounding network (15 MΩ//4.7 nF) is provided for each channel. This network causes a leakage current if the sensor is referenced to ground.
Sensor reference to ground (continued)
  • Use of floating sensors (recommended mounting - with no reference to ground):
    an internal network for each channel grounds the cold points of the sensors.
Sensor reference to ground (continued)
  • Use of sensors referenced to ground:
    If the following characteristics are respected, then each sensor can be assigned a voltage rate according to ground:
    • must be lower than the safety voltage
    • setting a reference voltage from a sensor point will cause a leakage current to be generated. If several analog TBX modules are used, measure the total leakage current and check that it will not interfere with the application. The RC grounding network has a value of 15  MΩ, 4.7 nF, for a 48 volt reference voltage, in relation to ground, with a current of 3.8 mA being created.
Specific cases
The following table describes the precautions to be taken in the specific case of thermocouple, current, and temperature probe inputs.
Specific cases Precautions to take
Thermocouple inputs
The thermocouple/terminal block connections must be carried out using compensation cables adapted to the type of thermocouple.
Preferential installations for thermocouple measurements are the following:
  • standard convection with an ambient temperature gradient of < 5 °C/hour:
    The TBX AES 400 will be mounted horizontally uninsulated as a base and/or as an extension with a minimum clearance of 150 mm in height (D) and 100 mm in width (d). The best results are obtained at an ambient temperature of 25 °C. The module supply voltage must be 24 V DC.
  • standard or forced convection with an ambient temperature gradient of > 5 °C/hour:
    the TBX AES 400 will be horizontally mounted as a base in an AC1-GV 263016 enclosure. The guaranteed performances are the same as in the case for standard convection with an ambient temperature gradient of < 5 °C/hour.
    The module supply voltage must be 24 V DC.
Current inputs
When the input signal is a current of 0/20 mA or 4/2 0mA, it is necessary to connect a resistance of 250 Ω - 0.1 % - 1/2 Ω - 25 ppm / °C (TSX AAK2 : packs of 4 resistors) to terminals R+ and R- which are assigned to the channel.
Temperature probe inputs
2 or 4 wire temperature probes may be used.
For Pt100 2 wire probes, the probe can be at a distance of 2.50 m without affecting the measurement (1) if cables with a 2 mm2 cross-section are used.
For Pt1000/Ni1000 2 wire probes, the probe can be at a distance of 25 m without affecting the measurement (1) if cables with a 2 mm2 cross-section are used.
Note: the current source is common to all temperature probes which are then mounted in series.
The diagram opposite shows how the connecting terminals facilitate 4 wire wiring.
A fault in the wiring of the current source or in one of the temperature probes will lead to there being a fault on all the channels, which will be seen as a sensor connection fault.
Channels 0, 1 and 2: 4-wire Pt100 probe.
Channel 3: 2-wire Pt100 probe.
Key:
(1)
Beyond this, the wire resistance systematically causes an error which can be corrected by the sensor alignment procedure.
CAUTION
DEGRADATION OF PERFORMANCES
Any use which does not respect the thermocouple input recommendations (orientation, ambience, module power supply) will result in a degradation of performances of the TBX AES 400. However, in stable ambient temperature conditions, it is possible to reduce error by carrying out a sensor alignment.
Failure to follow these instructions can result in injury or equipment damage.