Design And Function; Principle Of Operation - ABB TEIP11 Operating Instructions Manual

8 TEIP11, TEIP11-PS I/P SIGNAL CONVERTER | OI/TEIP11/TEIP11-PS-EN REV. M

3 Design and function

The I/P signal converter converts standard electrical signals, e.g.
4 to 20 mA to 0.2 to 1 bar (3 to 15 psi). It therefore forms a
connecting link between electrical/electronic and pneumatic
systems. The signal conversion process is similar to the
patented force balance method.
Special features of the I/P signal converter are its relatively
small dimensions and outstanding operational stability when
subjected to shock and vibration. The I/P signal converter can
be subjected to loads up to 10 g with less than 1 % effect on
function.
The housings are available in a variety of designs to meet your
installation requirements. For potentially explosive conditions,
devices offering intrinsically safe operation or with a flameproof
housing enclosure are available with international approval
certificates for use worldwide.
Various ranges can be supplied on the input side and the output
side for signal conversion (see Additional documents on
page 16).
The device requires only compressed air for the power supply.

Principle of operation

1 Coil
2 Yoke
3 Air gap
4 Magnet
5 Flapper
6 Air nozzle
7 Throttle
Figure 1: Schematic structure
8 Converter stage
9 Lever arm
j Potentiometer
k Resistor
l Filter
m Air supply
Force balancing takes place at the lever arm, which is mounted
with a tension band. The coil and yoke generate a magnetic field
in the air gap, which applies a force to the magnet on the lever
arm. The force changes in proportion to the current (input
signal) flowing through the coil.
A counterforce is applied on the other side of the lever arm,
through the dynamic air pressure present at the nozzle and the
flapper. The force is controlled in such a way that a balance of
the two torques is achieved. If a torque imbalance occurs, the
lever arm rotates. This rotation changes the air gap between the
nozzle and the flapper and, thus, the dynamic air pressure. Air is
permanently supplied to the nozzle through the throttle. The
converter stage takes the dynamic pressure and guides it to the
output as a 0.2 to 1 bar or 3 to 15 psi signal.
Supply air
During operation the pneumatic unit needs a steady supply of air
in accordance with the device specifications. The zero point
setting is adjusted by turning the tension band suspension, and
the range setting is adjusted via the potentiometer.
Filter
The filter prevents malfunctions caused by polluted supply air.
Note that the filter capacity is only sufficient for collecting dirt
that occurs occasionally (e.g. residual dirt in the pipe during
initial commissioning). It is no substitute for proper air
conditioning.
Special features
Special features of the I/P signal converter TEIP11, TEIP11-PS
include its relatively small dimensions and outstanding
operational stability when subject to shock and vibration. The
stability is due to the light weight (only around 100 mg) of the
moving system, which consists of the lever arm with the magnet
and the flapper with balancing weight.
Available versions
The available versions of the I/P signal converter and accessories
can be found in the data sheets. The data sheets also indicate
each item's order number.