Tempco TEC-9300, Инструкция по эксплуатации, Страница: 20 / 92

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2–6 Thermocouple Input Wiring
The thermocouple input connections are shown in figure 2.5. The correct type of
thermocouple extension lead-wire or compensating cable must be used for the entire
distance between the controller and the thermocouple, ensuring that the correct
polarity is maintained throughout. Joints in the cable should be avoided, if possible.
If the length of the thermocouple plus the extension wire is too long, it may affect
the temperature measurement. A 400 ohms K type or a 500 ohms J type thermocou-
ple lead resistance will produce approximately 1°C temperature error .
The color codes used on the thermocouple extension leads are shown in table 2.1.
2–4 Power Wiring
The controller is supplied to operate at 11–26VAC/VDC or
90–264VAC. Check that the installation voltage corresponds to
the power rating indicated on the product label before connecting
power to the controller .
2–5 Sensor Installation Guidelines
Proper sensor installation can eliminate many problems in a
control system. The probe should be placed so that it can detect
any temperature change with minimal thermal lag. In a process
that requires fairly constant heat output, the probe should be
placed close to the heater. In a process where the heat demand is
variable, the probe should be close to the work area. Some exper-
iments with probe location are often required to find the opti-
mum position.
In a liquid process, the addition of a stirrer will help elimi-
nate thermal lag. Since a thermocouple is basically a point
measuring device, placing more than one thermocouple in par-
allel can provide an average temperature readout and produce
better results in most air-heated processes.
The proper sensor type is also a very important factor in
obtaining precise measurements. The sensor must have the
correct temperature range to meet the process requirements. In
special processes, the sensor might have additional require-
ments such as leak-proof, anti-vibration, antiseptic, etc.
Standard sensor limits of error are ±4°F (±2°C) or 0.75% of
sensed temperature (half that for special) plus drift caused by
improper protection or an over-temperature occurrence. This
error is far greater than controller error and cannot be correct-
ed on the sensor except by proper selection and replacement .
This equipment is
designed for installation
in an enclosure which provides
adequate protection against
electrical shock. Metal enclo-
sures must be connected to
earth ground.
Local requirements regard-
ing electrical installation
should be rigidly observed.
Consideration should be given
to prevent unauthorized per-
sonnel from gaining access to
the power terminals.
Thermocouple Cable British American German French
Type Material BS ASTM DIN NFE
Copper (Cu)
+ white + blue + red + yellow
T
Constantan (Cu-Ni)
– blue – red – brown – blue
*
blue
*
blue
*
brown
*
blue
Iron (Fe)
+ yellow + white + red + yellow
J
Constantan (Cu-Ni)
– blue – red – blue – black
*
black
*
black
*
blue
*
black
Nickel-Chromium
+ brown + yellow + red + yellow
K (Ni-Cr)
– blue – red – green – purple
Nickel-Aluminum
*
red
*
yellow
*
green
*
yellow
(Ni-Al)
R Pt-13%Rh, Pt
+ white + black + red + yellow
S Pt-10%Rh, Pt
– blue – red – white – green
*
green
*
green
*
white
*
green
Pt-30%Rh
Use + grey + red Use
B
Pt-6%Rh
Copper – red – grey Copper
Wire
*
grey
*
grey Wire
Table 2.1 Thermocouple Cable Color Codes
*
Color of overall sheath