Dwyer DMF - Manual (Page 5)

Attitude sensitivity of the Mass Flow Controller is + 15 F . This means that the gas flow
path of the Flow Controller must be horizontal within those stated limits. Should
there be need for a different orientation of the meter, re-calibration may be neces-
sary. It is also preferable to install the DMF transducer in a stable environment, free
of frequent and sudden temperature changes, high moisture, and drafts.
Prior to connecting gas lines inspect all parts of the piping system including fer-
rules and fittings for dust or other contaminants.
Be sure to observe the direction of gas flow as indicated by the arrow on the front
of the meter when connecting the gas system to be monitored.
Insert tubing into the compression fittings until the ends of the properly sized tub-
ings home flush against the shoulders of the fittings. Compression fittings are to
be tightened according to the manufacturer's instructions to one and one quarter
turns. Avoid over tightening which will seriously damage the Restrictor Flow
Elements (RFE's)!
DMF transducers are supplied with standard 1/4 inch (DMF 41401-41433) or 3/8
inch (DMF 41842), or optional 1/8 inch inlet and outlet compression fittings which
should not be removed unless the meter is being cleaned or calibrated for a new
flow range.
Using a Helium Leak Detector or other equivalent method perform a thorough
leak test of the entire system. (All DMF's are checked prior to shipment for leak-
age within stated limits. See specifications in this manual.)
2.2 Electrical Connections
DMF transducers require a +15VDC and -15VDC power supply to operate.
Additionally, a readout panel meter, digital multimeter, or other equivalent device
is required to observe the flow signal in analog mode. A variable analog 0-5VDC
reference input is required for DMF models to operate in analog mode. The Dwyer
SDPROC accessory Command Modules offer a convenient and compact means
to fulfill these needs.
DMF is supplied with a 25 pin "D" connector. Pin diagram is presented in figure b-2.
2.3 Communication Parameters and Connections
Baud rate: 9600 baud Stop bit: 1
Data bits: 8 Parity: NON
RS-232 option: Crossover connection has to be established:
Pin 11 (TX) of the “D” connector has to be connected to RX
(pin 2 on the DB9 connector).
Pin 24 (RX) of the “D” connector has to be connected to TX
(pin 3 on the DB9 connector).
Pin 20 (Common) of the “D” connector has to be connected
to GND (pin 5 on the DB9 connector).
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