STRAIN CONTROL UNIT SPECIFICATIONS
This unit automatically carries out expansion of the pressuremeter at constant rates of strain. A wide choice of rates of strain is provided, both up and down, and any value of strain may be held constant indefinitely.
The Unit is offered in three versions. One has a maximum pressure rating of 4MPa and is made as a single unit incorporating the magnetic valves into the case containing the electronics.
The High Pressure version of the Unit has a maximum pressure rating of 10 MPa. This is constructed in two parts with an electrical cable connecting them. The main unit contains all the electronics. The magnetic valves Unit are carried in a separate box .
A third version is used with the Cone or Full Displacement Pressuremeter. It has a maximum pressure of 4 MPa but much faster strain rates.
In all Units the maximum rate of pressure change is adjustable to suit the soil being tested.
The Units are constructed in watertight cast aluminium alloy boxes. They are battery powered usually from the 12 volt car battery which supplies the Pressuremeter. All electronic connections are made with watertight military grade plugs and sockets. The gas supply is controlled by magnetic valves. All operations and adjustments to the controls of the strain control unit are shown by indicator lights.
Power Requirements: 12 - 24 volts DC. The unit draws 550 mA. In normal operation the unit will operate from voltages of 10 - 30 volts.
Connections: Watertight 4 mm sockets to the total strain outputs of the Electronics Box.
Quick Release connectors to the gas supply and to the Pressuremeter.
Controls: STRAIN RATE SWITCH -Standard Units: 0.1%, 0.2%, 0.5%, 1%, 2% suitable for per hour or per minute
HIGH PRESSURE UNIT: seven rates 0.1%, 0.2%, 0.5%, 1%, 2%, 5%, 10% per minute.
CONE PRESSURE UNIT: the strain rates are five times the rates for the Standard Unit
UP/HOLD/DOWN - controls the direction of strain.
STRAIN ZERO - a potentiometer adjustable for accurate setting of zero strain.
PRESSURE RATE SWITCH - Standard Units and Cone Pressure Units have five rates
of pressure change from
14 and 240 Kpa/min High Pressure Unit has seven rates of pressure change
from 25 to 1500 KPa/min.
PRESSURE ZERO - potentiometer adjustable for accurate setting of zero pressure.
RUN/RESET - starts a test and resets the unit into a safe condition at the end of a test.
Dimensions: Main box 330 mm x 230 mm x 150 mm
Valve Box 230 mm x 100 mm x 190 mm
Weight: 7.4 Kg. + 2.0 Kg for Valve Box
Mechanical Protection: Watertight, desiccated. Shockproof - all internal
connections
are hard-wired and contents are mounted in foam plastic.
In case of gas leakages the box has a safety valve to prevent it
becoming pressurised.
Maximum Strain:
The standard model of strain control unit has a maximum strain capacity
of 10%. This is equivalent to a Total Strain output of
600 mV from the Electronics Box. The unit can also be supplied
with a 15% maximum strain capacity, equivalent to a Total Strain input of
900 mV. Units for Cone Pressuremeters go to 50% radial strain
Leads:
The unit is supplied with leads and connectors for the sockets used and with
the appropriate quick release connection for gas.