Measuring Principle
The dynamometric scale focuses its measuring principle on a primary lever.
The charge of the water to be measured works on one of the arms of the lever, by means of a pressure/force system of transduction.
A mobile roman, directed by a micrometric screw, runs along the lever’s arm that is opposite the charge application.
The equilibrium position shows the measure of the applied charge, and therefore of the level to be measured.
When the system is at rest, the end of the arm of the lever on which the roman acts is in equilibrium in the action field of two magnetic sensors.
Each movement away from the lever’s equilibrium position causes an imbalance in the magnetic circuit; this activates the command motor of the micrometric screw by means of a special electronic circuit, which in turn moves the mobile roman until it regains its electrical and mechanical equilibrium.
A mechanical counter, with the same axial as the micrometric screw, counts the number and the fraction of turns necessary to bring the mobile roman to the new position of equilibrium. The reduction ratio between counter and screw is enough to reestablish the value of the level, a value which is expressed directly in centimetres.
The system is also equipped with an absolute encoder in Gray code, 13 bits, which allows the digitalization of the data for remote reading.
The system is designed for a maximum reliability and accuracy. For example, the pressure/force transduction is constructed with a sliding piston with a calibrated diameter, maintained in continuous rotation thanks to an agitating motor.
The piston works in oil and is subjected to the pressure of the water beater to be measured. In this way the system has virtually no inertia or friction.
Knife systems have been used, both for the fulcrum and the junctions of the roman and the piston; we guarantee that there is no phase displacement between the micrometric screw, the mechanical numerator and the absolute encoder.
Not having any contacts, the system used to locate the position of the arm ensures an elevated reliability in every condition.
As already mentioned, a 13 bit absolute Gray encoder is used for remote reading; this ensures a resolution of 1cm over a range of 81 m. The scale is equipped with magnetic end courses for safety.
The entire group is contained in a hermetically sealed case and maintained at constant temperature by a thermostat- heating element.
The dynamometric scale system allows the measurement of levels both with direct hydrostatic pressure measurements and pneumatic pressure measurements.
The basic instrument is the same for both versions; these only differ in their way of measuring pressure, as can be seen in the illustrative designs.
The instrumental electronics are contained inside the scale.
In the protection container of the mechanical groups, both the “electronic group” to control the sensors and the various components for regulation and protection are present. These are, for example:
The “fuse group”
The “control thermostat” for the heater
The chart for data serialization (optional)
The apparatus is already calibrated; therefore the operations to be performed on installation are limited to those regarding the connection of the connectors for signal and power supply transmission .
The data for the transmission is converted into serial RS232 or RS485
HYDROSTATIC VERSION
Necessary material:
- Scale
- Hydrostatic pressure taking group
- Restraint flange
- 2” Tube
- Hydrostatic pressure measuring group
For the connection between scale 4) and the acquisition unit it is used a multiple screened cable 4c.
PNEUMATIC VERSION
Necessary material
- Dynamometric scale
- Compressed air feeding group
- Pressure regulation frame
- Pneumatic taking pressure group
- Copper tube 10/12 mm
- Pressure measuring bell
Groups 1,2 and 3 are normally installed at the top of the dam, at a height near that of the maximum level of the reservoir.
The connection between the scale and the acquisition unit is ensured by means of copper tubes, that have a diameter of 10/12mm.
The connectors necessary to join the various groups are included with the respective units.
Groups 1) and 2) are generally placed in alarm situations.
To join scale 4) and the ML81B unit, a multiple screened cable is used (19c for parallel transmission, 4c for serial transmission).
Technical Features
| Measuring Range |
80 m or 140 m |
| Encoder Resolution |
1 cm (range 80m); 2cm (range 140m) |
| Sensibility |
1 cm (range 80m); 2cm (range 140m) |
| Accuracy |
± 1cm on all range; ± 2 cm on all range |
| Standard output code |
13 bit parallel Gray – disconnected
Serial Gray with transmission in current loop 0/20mA |
| Power supply voltage |
Standard : 24Vca ±10%; 50 Hz;
Optional : 110/220 Vca ±10% |
| Consumption with heaters switched off |
50VA |
| Maximum consumption with heaters switched on |
100VA |
| Tracking rate of the level change |
22 cm/min (66cm/min) |
Technical Assistance
If you have any requests or questions about our instruments or if you have special needs that require different solutions from the standard, please contact us. Our team will provide all the necessary information and will be very happy to work with you to study, develop and customize instruments and solutions suitable for your specific needs.
All information in our datasheet is subject to change without prior notice.
Please check the datasheet/details carefully and contact Pizzi Instruments for further information
