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Signal Conditioning Circuits
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Friday, 03 December 2010
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A selection of compatible electronic circuits designed to
condition raw signals from the sensors into a more usable form, usually a D.C.
voltage level for data acquisition or control purposes. These circuits are laid
out on the front panel in clearly labeled functional blocks.
Differential Amplifier
A dual input differential amplifier with variable gain and
set zero controls.
Range Switch: x1, x10, x100.
Gain: continuously variable between 0.1 and 1.0
Set Zero: Offsets output in range of ± 5 V.
Capacitance Bridge
An a.c. capacitance bridge with a built-in 80 kHz oscillator. The variable
capacitor on the Linear Assembly forms one arm of the bridge.
Comparator
Provides a comparison between two signals such that the output is either high
or low depending upon which is more positive.
An output relay allows the output to control the supply to power devices such
as the SIS motor or some other compatible external device.
Phase Sensitive Detector
A phase sensitive detector producing a D.C. output signal proportional to the
phase of the input compared to a reference signal.
Includes a 3 kHz oscillator to energies the LVDT primary winding as well as
providing 0 and 180 references.
4-bit Decoder
Designed for use with the 4-bit Gray Scale Encoder mounted on the SIS rotary
shaft to give rotary position measurements. Resolution 22.5 (360/16)
The Decoder inputs the 4 individual bits of data directly from the Gray Scale
Encoder and converts these into a binary code using a Gray to Binary Decoder.
The binary code is then converted by the 4 Bit DAC (Digital to Analogue
Converter) into an analogue voltage signal in the range of 0-5 V. This
corresponds to a complete revolution of the shaft of 360. With the 4-bit
resolution of the encoder this signal will actually comprise a series of 16
steps corresponding to angular positional changes of 22.5.
Filters
To remove unwanted frequencies from a signal. Filter options are: low pass,
band pass and high pass.
Differencing Amplifier
Amplifier with two inputs - one inverting (-) and one non-inverting (+). The
output is the difference between the two inputs. Amplifies in the range
(nominal) 1 to 50 as set by the gain control knob.
V to F / F to V Converter
The V to F circuit converts an input signal in the range of 0 to 5 V into a
corresponding frequency of 0 to 500 Hz. The F to V circuit converts a 0 to 500
Hz signal at its input into a 0 to 5 V signal at its output.
An optical link is provided that may be switched in to allow the frequency
modulated signals to be transmitted through the medium of a fiber optic cable
connecting the two converters rather than a wire.
V to I / I to V Converter
The V to I / I to V Converter is designed to illustrate the standard
industrial technique of data transmission using current sources to overcome
signal attenuation losses in a cable when using analogue voltage signals.
V to I Converter:
I to V Converter:
Current input in the range 4-20 mA produces a voltage
output signal in the range of 0-5 V.
A 0-500 ohm variable resistance is provided to simulate a length of cable
between the source and the receiver such that signal propagation over the
length of the cable can be investigated.
The value range of the resistance allows the limitations of the method to be
investigated once the source saturates.
Alternatively, the converters can be used to send and receive data using
external industrial sensors (not supplied) and with an actual ('real')
transmission lead with a maximum resistance of approximately 300 ohms.
Bridge Completion Resistors
A series of three 120 ohm precision resistors to be used in conjunction with
one or more of the strain gauges of the Linear Assembly, also 120 ohms, to
produce strain bridges of varying sensitivity.
Power Supply Input/Output
This section inputs the power supply from the mains/d.c. converter supplied
and then provides the individual specialist supplies needed to energies the
various sensors, signal processing circuits and actuator (motor) of the SIS.
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Panel Meter
3 digit voltage/frequency meter.
Range: 0 ± 10 V, 0-500 Hz.
Input switch able.
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PC Interface
12-bit A to D/D to A with a sampling frequency up to 10 kHz depending on PC
specification. Provides 1 analogue to digital (A to D) input and 1 digital to
analogue (D to A) output.
The input is switchable for a voltage input in the range ± 5 V, with a
resolution of ± 2.5 mV, or a current input in the range ± 500 mA, with a
resolution of ± 0.25 mA.
Also supplied with the Hardware Module as separate items:
Patching Lead Set
A selection of 2 mm patching leads to interconnect the selected sensor, signal
conditioning circuits and power supplies to create a wide variety of
experimental circuits.
Mains Lead
A universal mains lead with a built-in d.c. converter.
Input 110volts 1A.
Output: 12 V, 3 A. Regulated.
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