Omni Instruments DFS2 Instruction Manual

Instruction Manual 2009

DFS2 Doppler Flow Switch

DOPPLER FLOW SWITCH

INSTRUCTION

MANUAL

DFS2

(With rate indicator)

Rev 3

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Instruction Manual 2009

DFS2 Doppler Flow Switch

Doppler Flow Switch - DFS2
Introduction

The Doppler Flow Switch - DFS2 measures the velocity of fluids in pipelines using
a totally non-intrusive principle.

NB! It is intended for use with sewage, pulps, mining slurries, and other fluids which
contain in excess of 0,1% suspended solids or bubbles. The particle size for
successful operation must be greater than 100 microns.

The DFS2 enclosure is rated IP65. The flow switch includes a relay with adjustable
high and low set point controls, plus delay-on and delay-off adjustable timers. The
DFS2 requires 24Vdc, 115 or 230Vac power supply.

Two selectable flow ranges of 0 – 2 m/s, or 0 – 6 m/s are available, and the flow rate
is displayed on a bar graph indicator.

Connections and Adjustments

Removal of the flow switch cover will reveal the plug-in connections and various
adjustments, detailed as follows :-

Selector switch ‘S1’

Range selection

1
2

1 2 3 4 5 6 7 8 9 10 11 12

Figure 1

Trip point adjust

Lo

Hi

JP1

0-2 m/s
0-6 m/s

On Off

JP2

1 2

Lo

Hi

T1

T2

Latch selection

Timer adjust

Terminal No. Connection

1 Live / Positive
2 Neutral / Negative
3 Earth
4 Relay N.O
5 Relay N.C
6 Relay Common
7 To reset contact
8 To reset contact
9 Sensor Tx (Yellow)
10 Screen Tx (Green)
11 Screen Rx (White)
12 Sensor Rx (Brown)

Rev 3

1

Instruction Manual 2009

DFS2 Doppler Flow Switch

Connections

Sensor

Power Input

Relay

Latch Selection

: Connect the sensor to the 4-way terminal

plug as indicated in Figure 1 Terminal No’s 9
to 12.

: Check that the operating voltage of the flow

switch is correct, (i.e. 24Vdc, 115Vac or
230Vac) before connecting the power supply.

: The relay has a changeover contact, which

can be used for pump control, or simply to
initiate an alarm condition. The single control
relay will operate when the flow measured is
outside the high or low trip settings and can
be configured to operate with or without
“latch”.

: JP2 Position 1 – ON (latch/reset)

• Relay energised in normal conditions
i.e. between high and low limits giving
a failsafe mode.

• In alarm condition the relay will
deenergise and latch in the
deenergised position.

• Close reset contact (7 & 8) to reset
relay to energised position. Resetting
will also reset timer T2.

• If alarm condition remains after T2
timer times out the relay will again
deenergise and latch.

• If used for pump protect either power
the DFS2 from the pump circuit or
close reset contact allowing normal
flow conditions to be established
before T2 timer times out.

Position 2 – OFF (No latch/reset)

• Relay is deenergised in normal
conditions i.e. between high and low
limits.

• In alarm conditions the relay will
energise.

Rev 3

2

Instruction Manual 2009

DFS2 Doppler Flow Switch

Adjustments
Range Selection : (refer JP1)

Range 1 (0 – 2 m/s) :- Jumper in position “1”
Range 2 (0 – 6 m/s) :- Jumper in position “2”

Setting Low Flow Trip Point :

Move slide switch “S1” to “Lo” position. Adjust the low trip potentiometer until the
bar graph displays the required alarm setting as a percentage of the flow range
selected.

Example : Range 1 (0 – 2 m/s)
Bar graph display – 50%
Trip point setting – 1,0 m/s

Setting High Flow Trip Point

Move slide switch “S1” to “Hi” position and adjust high trip potentiometer to display
the required alarm setting.

NB Return slide switch to centre position for normal operation.
Delay-Off Timer T1 :

Under normal operating conditions the flow may fluctuate beyond the high or low trip
settings momentarily. The adjustable 0 – 60 sec. timer is adjusted with
potentiometer “T1”. Turn clockwise to increase the delay before the relay operates.

Delay-On Timer T2 :
If the flow switch is used for pump control it is necessary to over-ride the trip settings

during start-up, until the flow is established.
The adjustable 0 – 60 sec. timer is adjusted with potentiometer “T2”. Turn clockwise
to increase the delay before the relay operates.

Rev 3

3

Instruction Manual 2009

IF HORIZONTAL

DFS2 Doppler Flow Switch

Mounting The Transducer

a) Select a location for mounting the sensor at a point where the flow profile is fully

developed. Generally the principle of 10 pipe diameters of straight pipe upstream,
and 5 pipe diameters downstream will suffice, but should valves or bends exist
upstream of the sensor, the amount of straight pipe immediately upstream will need
to be increased.

b) Ensure that the sensor is mounted as far as

possible from potential noise sources, such as
pumps, control valves etc. and mount the
sensor at approximately 3/9 o’clock on the pipe

3 O’CLOCK POSITION ON PIPE

(if horizontal) to avoid errors due to air pockets

on top, or sediment at the bottom of the pipe.
c) Either vertical or horizontal pipe runs are acceptable for sensor mounting.
d) Before attaching the transducer head to the pipe surface, an area slightly larger than

the flat surface of the transducer must be cleaned to bare metal. (A small amount of

pipe pitting, even with spots of paint or rust, will not cause problems).
e) The transducer must be mounted accurately, parallel to the pipe axis, for correct

performance, and transducer to pipe contact should be along the centre line of the

transducer head.

f) Bonding to the pipe is achieved with silicone

coupling compound. Be sure to fill in any air

gaps that may remain at the pipe transducer

interface with additional compound.

A pipe clamp kit is included with the flow switch.

It includes silicone coupling compound, a

Neoprene rubber pad, and four polyamide 12

straps for pipe diameters up to 300 mm. In

applications with excessive vibration it is

recommended that the Neoprene rubber pad is

inserted between the pipe and the transducer.

GOOD

Coupling compound must be applied to both

sides of the pad.

Mounting the Switch

The DFS2 electronics is housed in a water resistant housing, which should be

mounted in a location where the ambient temperature is within the range stated in

the specifications i.e. -10°C to 50°C.

Rev 3

4

Instruction Manual 2009

DFS2 Doppler Flow Switch

Trouble Shooting

Relay Operates With No Flow

Possible Cause - Trip points set too low

- Vibration on pipe

Corrective Action - Adjust trip points above 0 m/s

- Relocate transducer

- Use Neoprene rubber pad in transducer
mounting

Rev 3

Relay Does Not Operate

Possible Cause - High trip point set below low trip point

- Unit faulty
Corrective Action - Adjust high trip point above low trip point

- Return unit to factory

Signal Strength LED Not Illuminated, or Flickering slowly

Possible Cause - No flow

- Insufficient suspended solids in fluid

- Bad coupling of transducer

- Incorrect transducer connections
Corrective Action - Confirm flow

- Inject air into pipeline

- Check transducer mounting

- Check transducer connections

5

Instruction Manual 2009

DFS2 Doppler Flow Switch

Specifications

Measuring Range : 0.3 to 2.0 m/s (1)

0.3 to 6.0 m/s (2)

Set Points : 0 to 100% of Range

Timer Delays : 0 to 60 seconds

Output : 1 Relay - 1Amp SPDT

Transducer Cable : 3 metre length

Temperature : Sensor -20 to 90°C

Electronics -10 to 50°C

Electronics : IP65 Polycarbonate

Rev 3

Enclosure 120 x 120 x 55mm

Power Input : 115/230V ac, 50Hz

24V dc +/-10%

Transducer : IP68 St/Steel

81 x 23 x 21mm

Indication LED’s : 10 LED bar graph

Range selection

Hi and Lo Alarm

Signal Strength

Failsafe Mode : Selectable

Pipe sizes : 25mm to 3000mm

Weight : 0.85kg

6