Digital Probe and Controller connected
Digital Probe
Controller
Principle of Operation
The patented measuring method used in the Digitrans Digital RF Probe uses digital measurements only with a self compensating system to eliminate temperature effects in the measurement head. The effects of the capacitance and conductivity on the probe are measured in terms of frequency and then these frequency readings are converted to engineering units (Brix, concentration etc as required) by a digital controller.
Description
The DIGITRANS digital radio frequency probe has applications in the Sugar Industry for the measurement of brix of massecuites in pans, or of liquors. The system uses measurements at two different radio frequencies, which are optimally combined to produce a signal representative of brix. This probe can be used on all products, and is especially suitable for use on Refinery Pans where the effects of varying ash content on measurements can be minimized.
The measurement system consists of a probe, (model T2, T3, or T4), which fits into an adaptor ring mounted on a vessel or pipe where measurements are to be carried out, and a separate control unit, (model C2C) into which two probes may
be connected.
The control unit provides power to the probes, receives measurement signals from the probes via single co-ax cables, and processes the measurements to produce outputs suitable for control.
The controller has a keypad used for calibration of the probes, and a digital display, which can provide a direct readout of brix.
Two methods of calibration can be used. The first involves using a calibrator to simulate product impedances.
The second method involves taking a number of samples, and keying the laboratory brix results into the controller. In this method, a regression is done automatically in the control unit to optimize combination of the R.F. measurements to produce an output calibrated in brix units.
Applications
The digital probe is used wherever a linear indication of accurate brix readings is required. It may be used on high and low purity solutions but is of greatest use in high purities. The different model probes are used as follows:
Model T2
Used in liquor, batch pans and refinery pans
Model T3
Used in continuous pans
Model T4
Used in batch pans
Calibration
The instrument can be pre calibrated with the general characteristic of the product if this is known or for greatest accuracy can be calibrated in situ in the process. The process liquor has to be taken through the entire brix range that is anticipated while samples are taken and calibration readings are recorded in the controller for each sample.The samples are then analysed for brix and the results of laboratory analyses are entered next to the corresponding frequency readings. The controller carries out a regression on this data after which the instrument is automatically calibrated using the coefficients produced by the regression. The two outputs may be calibrated differently for two different products or in some cases it is possible to measure two different parameters on the same product. e.g. brix and ash.
Digitrans Probes
Models
Total Length
Wetted Length
T2
T3
T4
Probe Diameter
Probe Body material
Connection into Process
Probe Body Temperature
Probe Head Temperature
Electrical Connection
Cable to Controller
Power Consumption
Protection Class
422mm
577mm
507mm
26mm
316 Stainless Steel
Adapter flange welded to vessel. Bronze socket bolted to flange with O ring seal.
Max 120° C
Max 70° C
N type coaxial socket
RG 58 C/U 50 Ohm coaxial
Typically 60 mA 16 – 25 V DC
IP 65. PCB encapsulated in epoxy for added protection
165mm
320mm
250mm
Digitrans Controller - Model C2
Power Requirement
Probe Inputs
Program
Parameter Storage
Display
Keypad
Ambient Temperature
Outputs
Inputs
Isolation
Terminations
Protection Class
Accuracy
22 – 28 V DC – 300mA
2 off N type coaxial sockets
EPROM
Battery backed RAM
4 line alpha numeric LCD with backlight
16 keys – access through password
50° C
4 X 4-20 mA into 500 ohms
2 X 4-20 mA two wire loop powered temperature probes
Probe power isolated from ground and input power. 4-20 mA signals ground common with 24 Volt supply ground.
Screw terminals in separate compartment to electronics
IP65
+/- 0.1 brix with in situ calibration
