Integral DSC digital strain conditioning amplifier card provides high speed, high accuracy, direct feed of pressure to the computer system controlling the machine and logging and displaying the data
The DSC is a small, robust printed circuit board, designed and built using the latest surface mount technology, that will provide the excitation voltage for a strain gauge transducer, conditions the signal, and transmits it directly to the serial port of a computer via an RS485, RS232 or Can interface.
The RS485 and Can protocols allow a network of multiple transducers to be addressed from one serial port.
The fully-programmable DSC can operate at baud rates up to 230,400, data rates to 500 readings per second, data resolutions up to one part in 400,000 (or 2.5ppm), has built-in shunt calibration, linearisation tables, provision for a temperature probe, a digital input and digital output, and may be programmed to output in engineering units.
The CTPT is a testing instrument for determining the flow properties of fresh cement and concrete mixes, and is capable of giving meaningful engineering data about the mix.
The machine stirs the mix at a range of speeds, and the pressure in a hydraulic gearbox is recorded as a function of speed.
This pressure reading is related to the torque applied to the stirrer, and a plot of torque against speed generally shows a straight-line relationship that does not pass through the origin but, rather, intercepts the pressure axis at a positive value when the speed is zero.
This intercept value is a measure of the yield stress, ie the stress which must be exceeded before the mixture will flow.
The slope of the subsequent straight line is a measure of the viscosity or plasticity of the batch.
The new version of the CTPT is provided with both manual and computer control, with a purpose-written software package controlling the speed at a constant value, over a 'staircase' of a series of constant speeds each held for a selected period of time, or over a ramp, with speed changing linearly over a set period of time.
Full guarding is provided, together with a torque overload circuit, and a planetary gear attachment allows an impeller with a non-static axis to be used.
Said Celsum Technologies's MD, Roy Carter: "We chose the DSC as an easy-to-use way of converting the pressure signal from a strain-gauge transducer into a digital signal that could be read by the computer".
"It was much cheaper than buying an A/D converter card with an equivalent resolution".
"We mounted the DSC in a DSJ1 junction box, which is designed to protect the DSC to IP65 standard and to make wiring of the circuitry easy".
"We found it a simple matter to write a driver routine for the DSC into our Visual Basic software code, and extensive tests showed that the circuit was extremely reliable".
"We were very impressed with the fast speed of reading, and the on-board shunt calibration resistor, which allowed us to write a routine to automatically calibrate the sensor." Both the CTPT and the DSC are available from Celsum Technologies.
