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Operation
Models: DHT and DHCR
Temperature
The thermistor type temperature transducer is in contact with the oil flow and temperature is
displayed on the left hand side of the digital display. Temperature from the internal transducer
is displayed in the INT and TACH position; temperature from a remote turbine is displayed in
the EXT position. Pressing the °C/°F button toggles the display between Centigrade and
Fahrenheit, the unit selected is indicated by a cursor arrow.
Flow Meter
The Flow Meter comprises an axial turbine mounted in an aluminium block. The oil flow rotates
the turbine and its speed is proportional to the oil velocity. The revolutions of the turbine are
measured by means of a magnetic sensing head which feeds a pulse every time a turbine blade
goes by, to an electric circuit. The circuit amplifies the pulse, shapes it into square wave form
and has a digital output which is directly proportional to the number of pulses per second.
Flowrate is displayed in the right hand side of the digital display when INT or EXT are selected.
Pressing the units button switches the display to USGPM, IGPM or LPM and the selection is
indicated by a cursor arrow. When the flow rate falls below the minimum allowable "L" is
indicated on the display. When flowrate exceeds the maximum "H" is indicated on the display.
Tachometer
RPM is displayed in the right hand side of the digital display when "TACH" is selected on the
rotary switch. Pressing the units button switches to RPM or RPM/N indication. RPM assumes
the sensor provides one pulse per revolution of the shaft. RPM/N assumes the sensor provides
N pulses each revolution of the shaft. (See section on Tacho Generator) The value of N can be
varied (See section on programming).
Pressure Gauge
The pressure gauge has a spiral Bourdon tube and the gauge case is filled with glycerine to
ensure good dampening on pulsating pressures. The gauge is connected to the turbine block
by fine bore capillary tube. Testers with BUILT-IN load valve have a shuttle valve which
automatically reads the highest pressure in both directions of flow. A gauge port is provided in
the block for the addition of a low pressure gauge.
Fast Button
The fast button changes the update time of the display. In some situations quick response to
flowrate changes is required. With the cursor arrow highlighting the fast position, the update
time is approximately 1/3 second. Otherwise the update time is approximately 1 second. When
using the fast update, the display will be less stable on flow and shaft speed.
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