Intek 111D User Manual
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MAN114 REV C.wpd
SECTION 3
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OPERATION
3.1 START UP
Typically, the instruments come from the factory set up for the flow range of interest to the customer.
Following installation all that is required is to switch on power and initiate flow in the measurable flow
rate range. Flow sensors that are not calibrated directly on the fluid to be measured are so indicated in
this manual (SECTION 6) and require an in-line field calibration.
When power is first turned on, the output reading or signal will indicate full scale. After ten to forty-five
seconds (depending on flow range adjustment) the reading will stabilize. The instrument time constant
is generally between 4 to 12 seconds. Higher average flow rates will result in an observed faster
response time for a given unit.
3.2 GENERAL INFORMATION
The
Rheotherm instrument is compensated for a wide range of both ambient and flowing media
temperatures. However, abrupt changes in the temperature of the flowing material can cause the
instrument output to deviate from the true representation of flow rate. A proper reading is obtained only
when the transducer is in thermal equilibrium with the material. Typically, a 20°F abrupt change in
temperature may require 40 seconds to stabilize. Temperature ramps should be kept below 1°C/minute.
Rheotherm instruments are calibrated for a particular fluid, either at the factory or in the field. If the
fluid changes properties, the calibration changes. Therefore, once calibrated, do not allow fluid
properties such as density and viscosity to change (other than the intrinsic changes which occur with
temperature variation). If the fluid is changed, a recalibration may be attempted following the procedure
in SECTION 4.2. If this procedure does not provide a good calibration for the range of interest on the
new fluid, contact the factory.
3.3 OPTIONS (Refer to those Sections that apply to the instrument you have purchased)
1.
Analog Outputs — The unit will have a 0-5 Vdc, 0-10 Vdc or 4-20 mA output. See SECTION
2.3 Output for a discussion of the 4-20 mA output.
2.
Pulse Output — For either pulse option shown below, the factory standard for pulse frequency
is 2 KHz at full scale flow. Specific units of volume or mass per pulse may also be supplied.
Unless otherwise specified, the minimum pulse duration is 250
:
s.
A.
Open collector — The (+) connection on the output terminal is the collector of a 2N3904
NPN transistor. The (
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) connection is the emitter of the same transistor. The pulse rate
is linear with flow. Recommended maximum current is 150 mA; maximum voltage is
36V.
B.
Voltage pulse — This option uses the same circuit and connections as the open collector.
A 1k
S
pull-up resistor is added and tied to either a +5V or a +12V voltage source. This
provides a 0-5V or a 0-12V voltage pulse.