Kobold DF-**01 series, User Instructions

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DF-SEN
FM Rev. 12/13
KOBOLD Model DF Flow Sensor
User Instructions
CAUTION: For safety reasons, please read the cautionary information located at
the end of the manual, before attempting installation.
1.0 General
The KOBOLD DF flow sensor is intended for use in applications where flow
measurement is desired and the flow rate data needs to be transmitted as a pulse rate
output. The DF sensor contains a flow transducer which transmits a 0-100 Hz (nominal)
signal. This output frequency is linearly proportional to the flow measured by the
instrument and is transmitted by a bipolar transistor operating in an open collector
configuration.
The DF uses a paddle wheel to determine flow. The principle of operation is quite
simple; the paddle wheel rotation speed is calibrated for the maximum flow rate. This
rotation-flow relationship is linear in theory. In practice, theory is nearly borne out,
leading to a very precise measuring device. Any non-linearity is within the stated
measurement error of the device.
The paddle wheel approach to flow measurement has the advantage that the instrument
may be installed in both vertical and horizontal orientations (the axle, however, must
remain in a horizontal plane). Further, this measurement technique is relatively
insensitive to dirt in the medium (large quantities of ferritic contaminants, however, must
be avoided).