Siemens OCM III Instruction Manual

Instruction Manual November 2005

open channel

OCM III

Safety Guidelines: Warning notices must be observed to ensure personal safety as well as that of

others, and to protect the product and the connected equipment. These warning notices are
accompanied by a clarification of the level of caution to be observed.

Qualified Personnel: This device/system may only be set up and operated in conjunction with this

manual. Qualified personnel are only authorized to install and operate this equipment in accordance with
established safety practices and standards.

Unit Repair and Excluded Liability:

• The user is responsible for all changes and repairs made to the device by the user or the user’s

agent.

• All new components are to be provided by Siemens Milltronics Process Instruments Inc.

• Restrict repair to faulty components only.

• Do not reuse faulty components.

Warning: This product can only function properly and safely if it is correctly transported, stored,

installed, set up, operated, and maintained.

Note: Always use product in accordance with specifications.

Copyright Siemens Milltronics Process

Disclaimer of Liability

Instruments Inc. 2005. All Rights Reserved

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as designed and authored by Siemens Milltronics Process
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Inc. will not be responsible for the contents of partial or
whole reproductions of either bound or electronic
versions.

While we have verified the contents of this
manual for agreement with the
instrumentation described, variations
remain possible. Thus we cannot
guarantee full agreement. The contents of
this manual are regularly reviewed and
corrections are included in subsequent
editions. We welcome all suggestions for
improvement.

Technical data subject to change.

MILLTRONICS®is a registered trademark of Siemens Milltronics Process Instruments Inc.

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Email: [e-mail]

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© Siemens Milltronics Process Instruments Inc. 2005

TABLE OF CONTENTS

TITLE PAGE

ABOUT THIS ...

About This Manual 7

About the OCM-3 7

SPECIFICATIONS 9

Programmer 10

Transducer 11

Temperature Sensor 11

Cabling 11

Communication Software 11

INSTALLATION

Installing the OCM-3 13

Outline and Mounting 13

OCM-3 Layout 14

System Diagram 15

Installing the Transducer 16

Installing the Temperature Sensor 16

mA Output 17

Relays 17

Synchronization 18

Power Connections 19

Installing the Memory Back-up Battery 20

Communicating Via Computer 20

Installing the Programmer 20

7ML19985AB01 OCM III 3

START UP

General 21

Keypad 21

Legend 22

Initial Start Up 22

Fundamental Checks 25

OPERATION

Memory 27

Security 27

Units 27

Flow Calculation 28

Display 28

Damping 29

Relays 30

mA Output 30

Fail-Safe 31

Flow rate and Totalizing 31

Logging 32

Blanking 34

Temperature 34

Time and Date 34

Emulation Mode 35

Reset 35

Flow Velocity Input 36

Auxiliary Head Input 36

DC Output 37

Diagnostic Aids 37

7ML19985AB01 OCM III 4

‘D’ PARAMETER LISTING 39

‘F’ PARAMET ER LI STING 41

‘P’ PARAMETER LISTING 43

‘U’ PARAMETERS FOR P3 PRIMARY ELEMENT 51

Simple Exponential Devices, P3 = 0 53

BS-3680 Rectangular Flume, P3 = 1 58

BS-3680 Round Nose Horizontal Crest Weir, P3 = 2 60

BS-3680 Trapezoidal Flume, P3 = 3 62

BS-3680 U - Flume, P3 = 4 64

BS-3680 Finite Crest Weir, P3 = 5 66

BS-3680 Thin Plate Rectangular Weir, P3 = 6 68

BS-3680 Thin Plate V-Notch Weir, P3 = 7 70

Rectangular Weir (Contracted), P3 = 8 72

Round Pipe, P3 = 9 74

Palmer-Bowlus Flume, P3 = 10 76

H - Flume, P3 = 11 78

Universal Head vs. Flow, P3 =12 80

Rectangular Area x Velocity, P3 = 13 82

Trapezoidal Area x Velocity, P3 =14 84

Modified Trapezoidal Area x Velocity, P3 = 15 86

U Channel Area x Velocity, P3 = 16 88

Circular Area x Velocity, P3 = 17 90

Gull-Wing Area x Velocity, P3 = 18 92

Egg-Shaped Area x Velocity, P3 =19 94

Universal Area x Velocity, P3 = 20 96

APPENDICES

Maintenance 99

Error Codes 100

Communications 101

7ML19985AB01 OCM III 5

7ML19985AB01 OCM III 6

ABOUT THIS ...

ABOUT THIS MANUAL

Although the OCM-3 is very ‘approachable’ due its dialogue capabilities and intuitive
operation, the user should be familiar with this manual. This manual provides the user
with the necessary information required to install, start up and operate the OCM-3.

As the OCM-3 prompts the user with specific messages in a step-by-step fashion
during programming, the Start Up section serves essentially to compliment the
OCM-3. Start Up provides the user with instructions on the use of the programmer
and an overview of the programming requirements.

The ‘D’, ‘F’, ‘P’ and ‘U’ parameters listed in the Parameters section provide a quick
reference of the available programming and display parameters and their options. The
‘U’ parameter listing also provides mathematical and graphical details as a reference
to assist the user in programming the OCM-3 to the primary element being used. The
user is urged to rely on the manufacturer’s specification for obtaining and identifying
the primary element to which the OCM-3 is being applied.

In short,

If you want to know about

the product About This . . .

getting started Installation

how it works Operation

Read

Specifications

Start Up

Parameters
Appendices

ABOUT THE OCM-3

The OCM-3 is to be used only in the manner

outlined in this instruction manual.

The Milltronics OCM-3, Open Channel Meter, is an electronic instrument designed to
measure flow in open channels. It is housed in a polycarbonate enclosure and comes
with a removable programmer. As a system, it is used in conjunction with a remote
ultrasonic transducer (or auxiliary head measurement device) and a temperature
sensor.

The OCM-3 transmits a pulse signal to the transducer which is then emitted as
ultrasonic pulses. The pulses echo off the water surface and are then sensed by the
transducer. The time for a pulse to echo back from the water surface is temperature
compensated and converted into a measurement of head.

7ML19985AB01 OCM III 7

The OCM-3 converts the head measurement into flow rate, but also provides a
velocity sensor input for applications where a flow velocity measurement is required to
perform the flow calculation. The flow rate is totalized and stored in a comprehensive
data log to provide detailed flow analysis.

Programming of the OCM-3 allows the operator to select the flow calculation specific
to the primary measuring device (flume, weir or pipe). Special emphasis has been
placed on providing the most accurate flow calculations possible. To this end, specific
routines have been written to comply with the British Standards Institute’s
Specifications BS-3680. These routines calculate correction factors taking into
account second order effects such as approach velocity and boundary layer. In the
event that flow measurement is not covered by one of the flow calculations provided,
the OCM-3 can be programmed for flow measurement using one of the universal
flow calculations.

The OCM-3 provides serial communication for remote programming, data log retrieval
and print out for devices such as computers, PLCs and printers. Milltronics provides a
standard utilities software package for OCM-3 programming, remote display and data
retrieval. However, the user is not limited to the software provided. The user can
develop his own software program to perform tasks suited to his specific nee ds.

The OCM-3 features:

✓ multi field illuminated LCD, for ‘Flow and Total’ and ‘Relay Status’ display

✓ 0 or 4 to 20 mA output

✓ three multipurpose relays, including remote totalization

✓ 1 to 24 months data log, subject to logging rate

✓ extensive serial communication, including RS-232

✓ removable infra-red programmer

✓ AC and DC (bi-current) operation.

7ML19985AB01 OCM III 8

SPECIFICATIONS

Power: » dc supply: » 9 to 30 V DC, 8 W max

» ac supply: » 100/115/200/230 V ac ± 15%, 50/60 Hz,

20 VA max

Environmental: » location » indoor /outdoor

» altitude: » 2000 m max

» ambient temperature » – 20 to 50 °C (–5 to 122 °F)

» relative humidity » suitable for outdoor (Type 4X/Nema 4X

» installation category » II

» pollution degree » 4

Memory
back-up: » 3 V lithium battery (NEDA 5003LC or equivalent)

» operating life 1 year

» ‘SuperCap’ capacitor for back-up
during battery replacement

Range: » 0.3 m min to 1.2 m max ( 1 to 4 ft)

and / or

IP65 enclosure)

0.6 m min to 3 m max (2 to 10 ft)

Resolution: » 0.2 mm (0.007")

Accuracy: » ±1 mm/m, calculated error less than 0.02%

Temperature
Compensation: » external sensor to compensate over

the operating range

Programming: » via supplied programmer and

communication link

Inputs: » velocity sensor and

auxiliary head » range: » 0 to 10 V dc

» resolution: » 2.7 mV

Outputs: » transducer drive: » 44 Khz, 400 Vpp pulses of 0.1 msec typical

duration at a 100 msec typical repetition rate.

» instrumentation: » range: 0-20 or 4-20 mA

7ML19985AB01 OCM III 9

» resolution: 5 uA
» maximum loading: 1 KΩ

» isolation: 300 V ac continuous

» relays: » 3 alarm/control relays

» 1 form ’C’ SPDT contact per relay, rated at

5 A at 250 V ac non-inductive or 30 V dc

» dc output: » +24 V dc

» 20 mA average to 200 mA at 1/10 duty

cycle max

Communication: » RS-232 or ± 20 mA bipolar current loop,300,

600, 1200, 2400, 4800, 9600 or 19200 baud

Data Logs: » variable rate on 1, 5, 15, 30 or 60 min or 24 hr

» 31 days minimum/2 years maximum

Display: » illuminated liquid crystal 5 x 7 dot matrix

display with 2 lines of 40 characters each

Enclosure: »Type 4X / NEMA 4X / IP65

» 209 mm W x 285 mm H x 92 mm D
(8.2" W x 11.2" H x 3.6" D)

» polycarbonate

Weight: » 2.3 Kg (5.1 lb)

Approvals: » CE *, FM, CSA

» MCERTS Class 1 open channel flow device with environment

operation limits at 35 °C (95 °F) at 93% relative humidity

SIRA MC 050058/01

PROGRAMMER

NRTL/C

Enclosure: » general purpose

Operating Temperature: » –20 to 50 °C (–5 to 122 °F)

7ML19985AB01 OCM III 10

» 67 mm W x 100 mm H x 25 mm D

(2.6" W x 4" H x 1" D)

» ABS plastic

Battery: » 9 V (ANSI / NEDA 1604, PP3 or equivalent) or

3V lithium battery

TRANSDUCER

Model: » XRS-5*

Refer to associated Transducer manual.

TEMPERATURE SENSOR

Model: » TS-2, LTS-1 or LTS-1C

Refer to associated Temperature Sensor manual.

CABLING

Transducer: » RG-62U coaxial

» maximum separation 183 m (600 ft)

» must be run in grounded metal conduit

mA Output: » Belden 8760 or equivalent

Synchronisation: » Belden 8760

Temperature Sensor: » Belden 8760, 1 pair shielded/twisted,

18 AWG or equivalent

» maximum separation 183 m (600 ft)

» can be run in conduit with transducer cable

Communication: » RS-232: » Belden 8770, 3 wire shielded, 24 AWG

or equivalent

» maximum separation 15 m (50 ft)

» Bipolar Current: » Belden 9552, 2 pair shielded/twisted,

18 AWG or equivalent

» maximum separation 1,500 m (5,000 ft)

*Note: The XRS-5 must be used with the TS-2 external temperature sensor when
operating with the OCM-3.

Velocity Input: » Belden 8760 or equivalent

7ML19985AB01 OCM III 11

Auxiliary Input: » Belden 8760 or equivalent

24 V Output: » Belden 8760

COMMUNICATION SOFTWARE

Milltronics Utilities Software on standard PC floppy disk for DOS 3.1 and up.

7ML19985AB01 OCM III 12

INSTALLATION

Installation shall only be performed by qualified personnel

and in accordance with local governing regulations.

INSTALLING THE OCM-3

The OCM-3 should be mounted in a clean, dry area that is: within the ambient
temperature range and suitable for the specified enclosure. The front cover should be
accessible for programming and viewing.

It is advisable to keep the OCM-3 away from high voltage or current runs, contactors
and SCR control drives.

Do not mount the OCM-3 in direct sunlight without the use of a sun shield.

This product is susceptible to electrostatic shock.

Follow proper grounding procedures.

OUTLINE AND MOUNTING

16 mm

(0.6")

209 mm

(8.2")

172 mm

(6.8")

267 mm

(10.5")

lid screws
(6 places)

285 mm

(11.2")

106 mm

(4.2")

91 mm

(3.6")

programmer

suitable location for

conduit entrances

Milltronics reccomends using a punch for making

holes in enclosure. Use suitable cable glands to

maintain ingress rating.

Non metallic enclosure does not provide grounding between connections.

13 OCM III 7ML19985AB01

mounting holes

(accessed under

lid 4.3 mm (0.17")

dia.,4 places

customer mounting

lid

enclosure

screw

Use grounding type bushings and jumpers.

OCM-3 LAYOUT

board A

display
board

board B

All field wiring must have insulation suitable for at least 250 V.

Hazardous voltage present on transducer terminals during operation.

dc terminals shall be supplied from SELV source in accordance
with IEC 1010-1 Annex H.

Relay contact terminals are for use with equipment having no accessible
live parts and wiring having insulation suitable for at least 250 V.

The maximum allowable working voltage between
adjacent relay contacts shall be 250 V.

14 OCM III 7ML19985AB01

SYSTEM DIAGRAM

OCM-3

mA output

relay output

auxiliary input

velocity input

Milltronics transducer,
see Specifications

Milltronics TS- 2,
temperature sensor

customer device

customer alarm,
pump or control
device

customer device

customer device

bi-polar current

(Milltronics communication)

Maximum syste m ca pability. Not all components or their maximum quantity
may be required.

15 OCM III 7ML19985AB01

RS-232

customer device

Milltronics CVCC

98/03/05

INSTALLING THE TRANSDUCER

Max cable run 183 m (600 ft) of
RG-62U or equivalent. Cable must
be run in a grounded metal conduit
with no other cabling (except
Temp. Sensor cable).

Ground shield at OCM-3 only.

Insulate shield at junctions to
prevent inadvertent grounding.

Basic Wiring – Transducer

Hazardous voltage present on transducer terminals during operation.

Note: When using the XRS-5 transducer with the OCM-3, use the TS-2 external
temperature sensor. The internal temperature sensor in the XRS-5 cannot be used.

INSTALLING THE TEMPERATURE SENSOR

In order to compensate for uniform
temperature change in the air
between the transducer and the flow
surface, the temperature sensor
must be connected to the OCM-3.

Maximum cable run 183 m (600 ft) of
Beldon 8760, 1 pair shielded/twisted,
18 AWG or equivalent.

Temperature sensor cable can be
run with the transducer cable in a
grounded metal conduit.

Ground shield at OCM-3 only.

Basic Wiring – Temperature Sensor

16 OCM III 7ML19985AB01

mA OUTPUT

RELAYS

isolated 0 or 4 to 20 mA output (P26) into 1 KΩ loa d maximum.
Wiring should conform to standard instrumentation practices.
Ground shield at OCM-3 only.

relays shown in de-energized state,
contacts rated at 5 A at 250 V
non-inductive.

n.c. com n. o. n.c. com n. o. n. c. com n. o.

All relays are certified for use in equipment where the short circuit capacity of the
circuits in which they are connected is limited by fuses having ratings not exceeding
the rating of the relays.

17 OCM III 7ML19985AB01

SYNCHRONIZATION

Where two to a maximum of twelve transducers will be sharing a common conduit the
OCM-3s should be synchronized. In order to synchronize OCM-3s:

» remove jumper J1 on board A on all but one OCM-3

» interconnect the SYNC terminal (TB1-20) of all OCM-3s. Insure that
all OCM-3s share a common ground (TB1-34).

18 OCM III 7ML19985AB01

POWER CONNECTIONS

The OCM-3 power supply accepts 100, 115, 200 or 230 V ac per switch SW1
(board B) selection and 9 to 30 V dc.

The OCM-3 operates either under ac or dc power, or both ac and dc live
simultaneously. If both ac and dc power are live, the OCM-3 normally draws power
from the ac supply. In the event that the ac supply fails, the OCM-3 then draws power
from the dc supply.

AC POWER

*

100/115/200/230 V ac, 50/60 Hz,

select voltage via switch on board B

* switch shown in
‘OFF’ position,
select appropriate
voltage.

The equipment must be protected by a 15 A fuse or

circuit breaker in the building installation.

A circuit breaker or switch in the building installation, marked

as the disconnect switch, shall be in close proximity to

the equipment and within easy reach of the operator.

DC POWER

19 OCM III 7ML19985AB01

nega tive dc input (T B1 - 24) is

9 to 30 Volt

dc input

tied to ground (TB1-34)

dc terminals shall be supplied from SELV source in accordance
with IEC 1010-1 Annex H.

INSTALLING THE MEMORY BACK-UP BATTERY

Disconnect power before installing or replacing the battery.

Do not install the memory back-up
battery until the OCM-3 is to be used.

The unit is supplied with one battery
package. Remove the battery from
the package and insert it into the
battery socket.

Refer to Operation \ Memory.

The memory battery, B1 (see Specifications) should be replaced yearly to insure
memory back up during lengthy power outages. An on board capacitor provides
one hour of memory retention in order to preserve the memory while the ba ttery
is being changed.

COMMUNICATING VIA COMPUTER

Refer to Communication.

INSTALLING THE PROGRAMMER

To program the OCM-3 via the Programmer, it must be placed into the front cover
recess of the OCM-3. The back of the Programmer has a magnetic plate which will
hold the programmer in place. It can be removed when programming is completed.

20 OCM III 7ML19985AB01

START UP

GENERAL

For the initial start up, it is advisable to use the programmer for programming the
OCM-3. The programmer transmits a coded infrared signal each time a key is pressed.

The OCM-3 is designed to automatically scroll through the ‘A’, ‘D’, ‘F’, ‘P’ and ‘U’
parameters in a structured sequence. The scrolling is interactive in that, depending on
the option chosen for a given parameter, subsequent parameters may be skipped or
modified. The user is thus prompted to satisfy only the parameters which are available
to him for the application he has chosen.

KEYPAD

numeric
entries with
decimal point

access to ‘D’, ‘F’,
‘P’ and ‘U’
parameters

negative

access to ‘A’ parameters
/ initiate s a printout while
viewing ‘Flow and T otal’

scrolls through selected
parameter options

scrolls

Forward

the parameters / enters
content of entry field

scrolls

Backward

parameters / clears content of entry field

through

through the

7ML19985AB01 OCM III 21

LEGEND

Press the associated programmer key:

Display shown on OCM -3:

Programmer key:

INITIAL START UP

After installation procedures have been completed, the OCM-3 may be powered up.
Upon initial powering up, the unit momentarily displays:

and then scrolls through the available languages:

The OCM-3 is asking which language you prefer to communicate in!

0

(0) language

F0 enter security code
< - - -

7ML19985AB01 OCM III 22

English

English language
selected

advance to ‘F0’

8 2 8

1

72

factory set security code

2.71828 must be entered

P0 language
0 English

P1 dimensional units
0centimeters

P0 language
0 English

if the wrong language
was selected, it may
be changed here

continue programming by
entering the desired options
and advancing until the
scroll returns to ‘P0’. It is
then assumed that the
user has entered all the
required parameters.

For optimum calibration accuracy, an ‘F13’ should be performed prior to accessing
‘F2’, the normal operating mode.

3

1

F13 auto zero calibration

enter the current head. The
OCM-3 calculates ‘P46’ and
automatically enters the value.

e.g. 1 6 0

01 6

F13 auto zero calibration
160

F13 auto zero calibration
0 completed

7ML19985AB01 OCM III 23

If data logging is desired, the time and date must be set.

4

F4 24-hr. time

e.g. 1141

4

1

1

1

F4 24-hr. time
1141

F4 24-hr. time
11:41:00 enter new time

11: 41 a.m.
seconds are always
assumed to be 00

time is displayed in
hh:mm:ss

,

F5 (ddmmyyyy) date

e.g. 12101492 October 12, 1492

0 1

4

9 211 2

F5 (ddmmyyyy) date
12/10/1492 enter new date

The start up procedure is now complete. Enter ‘F2’ to place the OCM-3 in the normal
operating mode.

2

Note: To save parameter values, return to RUN mode (F2) after programming.

The OCM-3 now displays the flow rate and total. Refer to Operation \ Display

7ML19985AB01 OCM III 24

FUNDAMENTAL CHECKS

For accurate determination of flowrate, accurate head measurement is essential.
Check the following and correct if necessary.

» check D5 for correct temperature at transducer location.

» check D9 for corre ct distance from transducer to head.

» check D0 for accurate head measurement.

7ML19985AB01 OCM III 25

7ML19985AB01 OCM III 26

OPERATION

Upon power up, the transducer is fired periodically as set by P36. A long interval
between measurements may be desirable in order to conserve power* when
operating the OCM-3 from a DC source of limited capacity.

The echo is processed to determine the head (D0). The flow rate (D1) is calculated by
the OCM-3 as a mathematical function (P3 and P4) of head or a function of head and
velocity (P42). The flow rate is then integrated to yield the totalized flow (D2). The
‘Flow’ and ‘Total’ fields which are displayed during the normal running mode (F2) are
also continuously updated.

Viewing or changing the content of a parameter (except F1, emulation) is done
without disturbing the acquisition, processing or logging of flow data (see \ Security).

*

restricted usage of display lighting (P14), relays (P15, 18 & 21), mA
output and communications will also conserve power.

MEMORY

During a power interruption, the memory back up will hold the programming, the log
and the totalizer values, and run the clock. The memory battery (B1) provides up to
one year of memory retention (see Appendices \ Maintenance).

Note: To save parameter values, return to RUN mode (F2) after programming.

SECURITY

The content of all ‘A’, ‘D’, ‘F’, ‘P’ and ‘U’ parameters can be viewed without having to
satisfy the security parameter, F0. However if it is desired to change the content of
any of these parameters, the security parameter must be satisfied (except for
resetting the running min/max displays, parameters D3/D4 and D6/D7).

Once security has been satisfied, a ccess continues for 5 minutes after the last key is
pressed or until F2 is re-entered.

The security code may be changed from its factory set value, 2.71828, by entering a
new value into F10. It is imperative that the new value be recorded, as the code can
not be viewed. If the code is lost, consult Milltronics.

UNITS

Programming of the OCM-3 involves setting the units of measure:

» P1 linear and velocity

» P2 temperature

» P5 flow rate and volume

If the units are changed during the course of operation, the change will be effected
through all associated parameters and displays and will rescale flow and total data
stored in the logs.

7ML19985AB01 OCM III 27

FLOW CALCULATION

Absolute vs. ratiome tric

The OCM-3 can be programmed to use eithe r of two methods (P4) for calculating flow
from the head measurement: absolute or ratiometric. The result is the same
regardless of the method used. The principal difference is the information that must
be entered in orde r for the OCM-3 to carry out the calculation. The user’s choice of
method may ultimately be based upon the information which is at hand. Refer to U
parameters for the primary element selected for a listing of the information required.

For the ratiometric method, it is usually sufficient that the user know the flow rate

) which occurs at maximum head (h

(Q

cal

On the other hand, absolute calculations require that the user enter information such
as: the physical dimensions of the primary element and the constant relating to units
of measure for both linear dimensions and flow rates.

e.g.

the general formula for flow through a single exponent primary element is:

cal

).

Q = KH

x

the specific formula for flow through a 45° V-notch weir is:

cfs = 1.03H

2.5

thus: Q = flow in cubic fe et per second

K = constant of 1.03
H = head in feet

The absolute method is not applicable to the following:

Palmer Bowlus flume
H flume

DISPLAY

The normal display during operation is the Flow and Total Display (F 2).

flow rate field

totalizer fie ld

7ML19985AB01 OCM III 28

relay / "no echo" field

status field

Flow Rate Field

Totalizer Field

flow rate

units, P5

total

multiplier, P32

Relay / No Echo Field

relay identification

under loss of echo
condition, "NO
ECHO" will
alternately flash

Status Field

relay status : 0 = relay de-energized

1 = relay energized
* = alarm state (indicated when

flashing)

The OCM-3 provides illumination for the LCD for easier viewing of the display.
Illumination can be set (P14) to be normally on or off, or automatic. When automatic is
selected, the lighting will automatically go on when keypad activity is sensed and then
extinguish after 15 seconds of inactivity.

For battery operation, set display lighting to off or auto.

DAMPING

The OCM-3 provides two separate damping functions: reading and mA output. Zero
or no damping allows fastest response while high or 100% provides the slowest
response. The damping is usually set to provide a reliable response without
sacrificing stability.

The reading damping, P13, dampens only the flow rate reading of the ‘Flow and Total’
display F2. The damping selections are: off, low, medium and high. Relay functions
associated with flow rate respond to the dampened reading values.

mA output damping, P27, dampens the change in the mA output. The parameter entry
is in seconds for spanning the 0 to 100% of the mA range selected (P26). Displays
and relay functions associated with the mA output respond to its
dampened value.

7ML19985AB01 OCM III 29

RELAYS

Three on board multipurpose relays are provided by the OCM-3. P15, 18 and 21 set
the respective functions for relays 1, 2 and 3. Depending on the function selected,
these parameters determine the need and configuration of the subsequent relay
control parameters, P16, 17 (relay 1); P19, 20 (relay 2) and P22, 23 (relay 3).

If the relay is to function as a driver for a remote totalizer or as a flow sampler contact,
the totalizer multiplier (P32) will be factored by the setpoint . Note that parameters
P16, P19, and P22 will default to zero. When a relay is set to totalizer (P32), you must
have the applicable parameter (P16 for relay 1, P19 for relay 2, or P22 for relay 3) set
to something other than zero (normally 1).

Example: For relay 1

Re la y totalizer factor =

totalizer factor (P32)

relay 1 setpoint (P16)

100 (P32=5)

=
2 (P16)

= 50 units/pulse

The status of each relay is shown in the display. Refer to \ Flow and Total Display.

For battery operation, have relays energizing on alarm.

mA OUTPUT

The OCM-3 provides a mA output (TB1-4/5) which can be assigned (P24) to
represent the measurement of flow, head, velocity or temperature. The associated
scaling, P25, is factory set to a value of ‘0’. This provides normal scaling with respect
to the assigned measurement.

Normal scaling for representation of flow, head or velocity is:

» 0 or 4 mA = 0

» 20 mA = maximum measurement value for: » P6

» P7: maximum head

Normal scaling for representation of temperature is:

» 0 or 4 mA = – 40 °C

» 20 mA = 60 °C

If custom scaling is required, the 20 mA corresponding value (other than 0) can be
entered into P25. The range (0 to 20 or 4 to 20 mA) and damping (see Damping) are
set via P26 and P27 respectively.

7ML19985AB01 OCM III 30

*

: flow rate

at maximum head

» P10: velocity
at maximum head

The mA function can be overridden for test purposes by setting the desired mA value
into F3. When the value is entered, the mA output will go to that value. When F3 is
exited, the mA output will revert to normal operation. Also, see \ Emulation Mode.

*In the case of absolute calculations (P4=0),

P6 is calculated by the OCM-3.

FAIL-SAFE

In the event of an echo loss, the fail-safe timer will begin counting. If the echo loss
duration surpasses that of the time set (P29), a ‘

No Echo

’ alert will be displayed in the
Status field (see \ Display). The mA output will respond (P30) by either holding the last
value or immediately going to a predetermined value (P31). The head and derived flow
will hold their last value and totalization and logging will continue, based on that value.
Upon resumption of a valid echo, the mA output will return to a value corresponding to
the present value of the measurement assigned, at the mA damping rate (P27).

FLOW RATE AND TOTALIZING

Flow rate

Calculation of the flow rate is ongoing. It is normally viewed under the Flow and Total
display (F2) with the decimal point set per P33. It can also be viewed under D1 as the
raw flow calculation. Data on the running minimum and maximum flows that have
occurred since the last reset can be viewed in two ways:

» F7 gives the running min/max flows and their time and date of occurrence since

the last reset. F7 is rese t by F8 but only after satisfying the security pa rameter F0.

» D3/D4 give the respective running min/max flow data , only, that have occurred

since they were last reset. D3/D4 are reset simultaneously by entering 0 into
either D3 or D4. D3 and D4 will then adopt the current flow rate and track the
running min/max values from that point on. The security parameter (F0) does
not need to be satisfied in order to reset D3/D4.

Flow data specific to a particular time and date can be viewed under the data log F14
(see \ Logging).

Totalizing

Totalizing of the calculated flow is ongoing. It is normally viewed under the Flow and
Total display (F2).

An auxiliary totalizer (D2) is provided for operator usage and is intended for short term
totalizing to a maximum count of 999999. It can be reset or preset independently of
the F2 totalizer after satisfying the security parameter (F0).

In order to adjust the rate of filling of the totalizer, the totalizer multiplier (P32) can be
set to an appropriate value. The totalizer can be reset via F11. Totalizing that is
specific to the time and date can be viewed under the data log F14.

The OCM-3 can be programmed to operate a remote totalizer by assigning any of the
relays (P15, 18 or 21) to act as a totalizer contact*. Under this function, the maximum
rate of contact closure is 2/sec with a closure duration of 200 msec**.

The totalizer count is set by the relay setpoint parameter (P16, 19 or 22 respectively).

*

**

Typically the totalizer should be set for 300 to 3000 counts per day at maximum flow.

7ML19985AB01 OCM III 31

Under low flow conditions, a cut-off head (P45) can be entered to avoid totalizing
flows occurring at or below the flow corresponding to the cut-off head.

LOGGING

The OCM-3 provides an extensive logging feature which can be viewed on the local
display or retrieved via the serial communication link. The logging rate (P39) can be
fixed or variable. The latter being useful in conserving logging space. The condition for
variable logging is determined when selecting the logging rate.

Variable logging rate conditions are catagorized as : rate of change of flow, percent of
maximum flow or percent of maximum head. Logging occurs at the normal (slower)
rate while the condition is less than the setpoint (P40). If the condition exceeds the log
rapid setpoint, the rapid rate of logging takes effect until the condition falls below the
log normal setpoint (P41).

The associated setpoint units are : % change of maximum flowrate per minute, % of
maximum flowrate and % of maximum head, respectively. The setpoints represent the
absolute value of the rate of change; that is, for either increasing or decreasing
flowrate. The OCM-3 does not recognize negative entries into P-40 and P-41.

Flow data is logged in 1/2 % increments from 0 to 110 % of maximum flow. Flows
above 110 % are logged as 110 %. Truncation of flows to 110 % does not apply to
daily totalization.

Log Capacity vs Rates

rate capacity

1 min 31 days

5 3 months

15 9 months

30 1 year

60 1.5 years

24 hr 2 years

e.g. 15 / 5 9 months max / 3 months min

Once the log is filled, the old data will be successively written ove r with the new
data being logged.

The log can be examined via F14. Viewing of the log is done by task and by method.
The viewing tasks are: daily flow totals, flow rates and min-max flow data for flow or
temperature. The viewing methods are: by first entry, by last entry and by specified
date. The scrolling keys are used to maneuver through the tasks, methods and
time of day.

7ML19985AB01 OCM III 32

Viewing the data log

The day totalizer (F14) does not use the master totalizer multiplier (P32). It is possible
that the daily total overflows. In such a case the display will show +++.++.

7ML19985AB01 OCM III 33

BLANKING

Blanking is used to ignore the zone in front of the transducer where ringing or other
false echo is at a level that interferes with the processing of the true echo. The
minimum blanking is factory set, but can be overridden by entering the desired
distance into P47.

Ringing is the inherent nature of the transducer mass to continue vibrating after the
transducer has been fired. Ringing decays to acceptable levels in the order of
milliseconds. Excessive cold or over tightening of the transducer mounting may
increase the ring time such that it appears as an echo during the receive cycle. This is
usually indicated by an incorrect high head reading. Excessive ring time may be
overcome by increasing the blanking.

TEMPERATURE

The temperature as currently registered by the temperature se nsor is viewed under
D5. Data on the running minimum and maximum temperatures that have occurred
since the last reset can be viewed in several ways:

F7 gives the running min/max temperatures and their time and date of occurrence
since the last reset. F7 is reset by F8 but only after satisfying the security
parameter F0.

D6/D7 give the respective running min/max temperature data, only, that have
occurred since they were last reset. D6 is reset by entering a value lower than D5,
and D7 is reset by entering a value larger than D5. D6 and D7 will then adopt the
current temperature value and track the min/max values from that point on. The
security parameter F0 does not need to be satisfied in order to reset D6 or D7.

Temperature data specific to the time and date can be viewed under the data log F14
(see \ Logging).

D14 indicates the resistance of the temperature sensor corresponding to the
temperature shown in D5.

TIME AND DATE

If the data logging features of the OCM-3 are to be used, the time (F4) and date (F5)
must be set. The day starts at 00:00:00 and ends at 23:59:59.

Adjusting the Time

If the clock time is advanced beyond the next anticipated logging time, the entry for
each missed logging time is filled with a code which indicates that the system was not
able to make entries at those times.

The daily total will be reduced proportional to the amount of time the day
was shortened.

If the clock time is set back beyond the preceding logging time, the previously logged
date will be written over with new data as the logging proceeds.

7ML19985AB01 OCM III 34

The daily total will be increased proportional to the amount of time the day was
lengthened.

Adjusting the Date

If the calendar is reset, the OCM-3 will adjust the log dates accordingly, taking into
account leap years and days per month.

EMULATION MODE

The flow calculation (P3/ P4) can be checked for accuracy by using the emulation
parameter F1. The head is entered and the corresponding flow is displayed. This
function is useful when troubleshooting discrepancies between the OCM-3 calculation
and the expected flow.

Relays assigned to functions associated with the emulation parameter respond to the
emulated flows.

The mA output does not track the emulated flows when P28 (mA output emulation) =

0. However, if it is required to do so, then the emulator parameter should be set to 1.

RESET

The following resets can only be e xecuted after satisfying the security access, F0.

Cold Start

If it is desired to reset all parameters, logs and totalizers to their factory setting, this is
done by forcing a cold start, F12 .

Master Totalizer

If it is desired to reset the master totalizer (F2), this is done by parame ter F11.

Data Log

If it is desired to reset the data log (F14), this is done by parameter F15.

Min/Max Log

If it is desired to reset the min/max log (F7), this is done by parameter F8.

7ML19985AB01 OCM III 35

FLOW VELOCITY INPUT

In some applications, the flow calculation for the chosen primary element requires a
velocity input. In this type of application, the transducer measurement is used to
calculate the cross sectional area of the flow. By multiplying the area with the distance
per time units of velocity, the volume per time units of flow are calculated. The
calculate d velocity can be viewed via D8.

The 0% and 100% limits of the velocity input must be scaled using parameters
P8 and P9.

» se le ct P8
» enter the voltage corresponding to zero velocity
» se le ct P9
» enter the velocity corresponding to 5 V

e.g. If the velocity sensor output is 1 V per m/ sec and the output is

scaled for 7 V at 100% velocity (7 m/sec), then enter 5 m/sec. If the
output is scaled for 4 V at 100% velocity (4 m/sec), enter 5 m/sec.

P8 and P9 can only be accessed if P3 has been set for an option that requires the use
of a velocity input. The input voltage level can be viewed via D12.

Voltage Input

typical 1 - 5 V signal from
velocity sensor.

Signal must be positive with respect to ground.

Velocity Input

AUXILIARY HEAD INPUT

Current Input

typical 4 - 2 0 mA signal from velocity sensor.
Add termina ting resistor.
e.g. 250 Ω for 1 - 5 V over 4 - 20 mA.

(additional to Basic Wiring)

In some applications, the transducer input (TB1-1/2) is not used to provide a signal for
head measurement. A typical example of this is an application which is beyond the 3
m (10 ft) range of the OCM-3. In such a ca se, the head could be derived from another
Milltronics level monitor or other compatible device.

The method of head determination is set by P42. The OCM-3 simply substitutes the
signal from the auxiliary device for the ultrasonic measurement provided by the
transducer. The programming and consequent flow calculation are performed
as normal.

7ML19985AB01 OCM III 36

The 0% and 100% limits of the auxiliary input must be scaled using parameters P43
and P44.

» se le ct P4 3
» enter the voltage corresponding to zero head
» se le ct P4 4
» enter the head corresponding to 5 V.

e.g. if the head output is 1 V per m and the output is scaled for 7 V at

100% head (7 m), then enter 5 m. If the output is scaled for 4 V at
100% head (4 m), enter 5 m.

P43 and P44 can only be accessed if P42 has been set for head determination by an
auxiliary device. The input voltage level can be viewed via D13.

Voltage Input

typical 1 - 5 V signal from
auxiliary device.

Signal must be positive with respect to ground.

Auxiliary Input

typical 4 - 20 mA signal from auxiliary device.
Add termina ting resistor.
e.g. 250 Ω for 1 - 5 V over 4 - 20 mA.

(additional to Basic Wiring)

Current Input

DC OUTPUT

The OCM-3 provides a 24 V DC output that can be used to supply power to a remote
customer device. The output is not isolated from the DC rails that supply the OCM-3
electronics and no overload protection is provided. As such, the output must not
operate beyond its specified capacity.

DIAGNOSTIC AIDS

D15 through D18 are diagnostic aids to Milltronics service personnel when
troubleshooting system problems.

D18 also serves as a performance indicator by displaying the number of valid echos
received as a percentage of the number of pulses being fired by the transducer. A low
value indicates that a large proportion of the pulses fired are not producing valid
echos. In such instances, the transducer should be checked for proper mounting and
aiming or the transducer wiring checked for excessive noise. If the value is zero,
shorted or opened transducer wiring may be suspect.

7ML19985AB01 OCM III 37

‘D’ PARAMETER LISTING

Refer to ‘Operation’ for details.

D0 head

D1 flow rate

D2 short total *

D3 maximum flow rate

D4 minimum flow rate

D5 temperature

D6 maximum temperature

D7 minimum temperature

D8 velocity

✧

D9 nominal target range

D10 analog milliamps

D11 internal DC volts

D12 velocity volts

✧

D13 auxiliary input volts

D14 tempe rature sensor ohms

D15 self-test checksum

D16 restarts

D17 exceptions

D18 valid echos per 100

7ML19985AB01 OCM III 39

*

security access required

✧

applicable to flow calculations requiring velocity sensor

7ML19985AB01 OCM III 40

‘F’ PARAMETER LISTING

Refer to ‘Operation’ for details.

F0 enter security code

F1 emulation mode

*

F2 run mode

F3 keypad to mA output

*

F4 show time

set time

*

F5 show date

set date

*

F6 software identification number

F7 view min/max data

F8 reset min/max data

F9 self check

*

F10 change security code

*

*

F11 reset master totalizer

F12 force a cold start

*

F13 auto zero calibration

F14 examine data log:

task: view daily totals

view flow rates

view min/max data

method:

first day

last day

specified da y

F15 clear data log

*

*

*

7ML19985AB01 OCM III 41

*

security access required

7ML19985AB01 OCM III 42

‘P’ PARAMETER LISTING

Refer to ‘Operation’ for details.

P0 language

0 = english

1 = french

2 = italian

3 = german

4 = spanish

P1 dimensional units

linear velocity

0 = centimetres centimetres per second

1 = inches inches per second

2 = feet feet per second

3 = metres metres per second

P2 temperature units

0 = Celcius

1 = Fahrenheit

P3 primary element

0 = exponential device

1 = BS-3680 Rectangular Flume

2 = BS-3680 Round Nose Horizontal Crest Weir

3 = BS-3680 Trapezoidal Flume

4 = BS-3680 U-throated Flume

5 = BS-3680 Finite Crest Weir

6 = BS-3680 Thin Plate Rectangular Weir

7 = BS-3680 Thin Plate V-notch Weir

7ML19985AB01 OCM III 43

8 = Rectangular Weir (contracted)

9 = Round Pipe

10 = Palmer Bowlus Flume

11 = H Flume

12 = Universal Head vs. Flow

13 = Rectangular Area x Velocity

14 = Trapezoidal Area

15 = Modified Trapezoidal Area

16 = U-channel Area

17 = Circular Area

18 = Gull-wing Area

19 = Egg-shaped Area

20 = Universal Area

P4 method of calculation

0 = absolute

1 = ratiometric

P5 flow rate units

flowrate

Velocity

x

Velocity

x

Velocity

x

Velocity

x

Velocity

x

Velocity

x

Velocity

x

volume

0 = litres per second litres

1 = cubic feet per second cubic feet

2 = imperial gallons per minute imperial gallons

3 = U.S. gallons per minute U.S. gallons

4 = imperial million gallons per day imperial million gallons

5 = U.S. million gallons per day U.S. million gallons

6 = cubic metres per hour cubic metres

7 = cubic metres per day cubic metres

P6 flow at maximum head

P7 height of maximum head

P8 volts in at zero velocity

P9 velocity at 5 volts in

P10 velocity at maximum flow

7ML19985AB01 OCM III 44

P13 display damping

0 = off

1 = low

2 = med

3 = high

P14 display lighting

0 = on

1 = auto off

2 = off

P15 / P18 / P21 relay 1 / 2 / 3 assignment

0 = not in service

1 = de-energize on loss of echo

2 = energize on loss of echo

3 = de-energize on high flow rate

4 = energize on high flow rate

5 = de-energize on low flow rate

6 = energize on low flow rate

7 = de-energize on high head

8 = energize on high head

9 = de-energize on low head

10 = energize on low head

11 = de-energize on high velocity

12 = energize on high velocity

13 = de-energize on low velocity

14 = energize on low velocity

15 = de-energize on high analog

16 = energize on high analog

17 = de-energize on low analog

18 = energize on low analog

7ML19985AB01 OCM III 45

19 = de-energize on low D11 volts

20 = energize on low D11 volts

21 = de-energize on high D11 volts

22 = energize on high D11 volts

23 = de-energize on low Aux. volts

24 = energize on low Aux. volts

25 = de-energize on high Aux. volts

26 = energize on high Aux. volts

27 = de-energize up control on head

28 = energize up control on head

29 = de-energize down control on head

30 = energize down control on head

31 = de-energize up control on analog

32 = energize up control on analog

33 = de-energize down control on analog

34 = energize down control on analog

35 = ( pulse ) flow totalizer

36 = ( pulse ) sampler by volume

37 = ( pulse ) sampler by time

38 = ( pulse ) by time of day

P16 / P19 / P22 relay 1 / 2 / 3 high setpoint

P17 / P20 / P23 relay 1 / 2 / 3 low setpoint

P24 mA assignment

0 = flow rate

1 = head

2 = velocity

3 = temperature

P25 If custom mA, 20 mA = ?

0 = normal

0 = custom

P26 mA span

7ML19985AB01 OCM III 46

0 = 4-20 mA

1 = 0-20 mA

P27 mA damping (secs)

P28 mA options (emulator tracking)

0 = don’t track emulator

1 = track emulator

P29 fail-safe time (secs)

P30 fail-safe analog mode

0 = hold last value

1 = assume value in P31

P31 fail-safe analog mA (default value)

P32 totalizer multiplier

0 = x 1/1000 (0.001)

1 = x 1/100 (0.01)

2 = x 1/ 10 (0.1)

3 = x 1

4 = x 10

5 = x 100

6 = x 1000

P33 flow rate display (decimal point)

0 = no decimal places

1 = 1

2 = 2

3 = 3

4 = 4

7ML19985AB01 OCM III 47

P34 printer mode

0 = never print

1 = interval to be in minutes

2 = interval to be in hours

3 = print once each day

P35 printer timing

P36 measurement interval

0 = 1 sec

1 = 15 sec

2 = 30 sec

3 = 1 min

4 = 5 min

P37 serial data rate

0 = 300 baud

1 = 600

2 = 1200

3 = 2400

4 = 4800

5 = 9600

6 = 19200

P38 site number

7ML19985AB01 OCM III 48

P39 data logging rate

fixed

0 = 1 min 3 = 30

1 = 5 4 = 60

2 = 15 5 = 24 hr

6 = 15/1 min (

variable

% flow / min

(

condition

)

) 19 = 60 / 1 (

flow

7 = 15 / 5 " 20 = 60 / 5 "

8 = 30 / 1 " 21 = 24 hr / 1 min "

9 = 30 / 5 " 22 = 24 hr / 5 min "

10 = 60 / 1 " 23 = 24 hr / 15 min "

11 = 60 / 5 " 24 = 15 / 1 min (

head

12 = 24 hr / 1 min " 25 = 15 / 5 "

13 = 24 hr / 5 min " 26 = 30 / 1 "

14 = 24 hr / 15 min " 27 = 30 / 5 "

)

)

15 = 15 / 1 min (

16 = 15 / 5 " 29 = 60 / 5 "

17 = 30 / 1 " 30 = 24 hr / 1 min "

18 = 30 / 5 " 31 = 24 hr / 5 min "

P40 log rapid setpoint

P39 variable logging condition units

% flow / min % change of maximum flow per minute

flow % of maximum flow

head % of maximum head

P41 log normal setpoint

P39 variable logging condition units

) 28 = 60 / 1 "

flow

32 = 24 hr / 15 min "

% flow / min % change of maximum flow per minute

7ML19985AB01 OCM III 49

flow % of maximum flow

head % of maximum head

P42 head determination

0 = by OCM-3

1 = by auxiliary device

P43 volts in for zero head

P44 head at 5 volts in

P45 low flow cut-off head

P46 range at zero head

P47 blanking distance

7ML19985AB01 OCM III 50

‘U’ PARAMETERS FOR P3 PRIMARY ELEMENT

The number of ‘U’ parameters required varies according to the primary element
chosen (P3) and the method of calculation (P4). The OCM -3 prompts the user by
displaying the next required parameter, insuring the programming is complete.

The following is a list of the specific primary elements to which the OCM-3 can
be applied.

Refer to the page covering your particular application; the rest may be disregarded.

P3 primary element

0 exponential device (e.g. proportional, V-notch, Parshall etc)

1 BS-3680 Rectangular Flume (ISO 4359)

2 BS-3680 Round Nose Horizontal Crest Weir (ISO 4374)

3 BS-3680 Trapezoidal Flume (ISO 4359)

4 BS-3680 U-throated Flume (ISO 4359)

5 BS-3680 Finite Crest Weir (ISO 3846)

6 BS-3680 Thin Plate Rectangular Weir (ISO 1438/1)

7 BS-3680 Thin Plate V Notch Weir (ISO 1438/1)

8 Rectangular Weir (contracted)

9 Round Pipe

10 Palmer-Bowlus Flume

11 H Flume

12 Universal Head vs. Flow

13 Rectangular Area

14 Trapezoidal Area

15 Modified Trapezoidal Area

16 U-channel Area

7ML19985AB01 OCM III 51

Velocity

x

Velocity

x

Velocity

x

Velocity

x

17 Circular Area

x Velocity

18 Gull Wing Area

19 Egg-shaped Area

20 Universal Area

x Velocity

x Velocity

x Velocity

The primary element must be installed in accordance with the manufacturers
recommendations and in accordance with all governing regulations.

7ML19985AB01 OCM III 52

SIMPLE EXPONENTIAL DEVICES, P3 = 0

‘U’ parameters required *

U0 = exponent

U1 = k factor (P4 = 0 only)

Typical Exponential Devices:

» Sutro (proportional) weir

» head measurement only

» Rectangular (suppressed) or Trapezoidal (Cipolletti) weir

» Kahfagi venturi

» Parshall flume

» Leopold Lagco

» Triangular (V-notch) weir

*

obtain from manufacturer’s specifications.

Reference

ABSOLUTE CALCULATION, P4 = 0¤

For flows that can be calculated by the equation:

q = k h

x

where q = flowrate x = exponent (U0)

k = constant factor (U1) h = head

RATIOMETRIC CALCULATION, P4 = 1¤

For flows that can be calculated by the equation:

cal

(h/h

q = q

where q = flowrate q

x

)

cal

h = head h

= flowrate at maximum head

cal

= maximum head

cal

x = exponent (U0)

Refer to manufacturers specifications for the exponent value.

¤

Refer to Operation \ Flow Calculation.

7ML19985AB01 OCM III 53

SIMPLE EXPONENTIAL DEVICES, P3 = 0

TYPICAL SHARP-CRESTED WEIRS

transducer *

minimum

3 x h

max

Typical Weir Profiles

V - notch or Triangular

U 0 = 2.5

Tra pezoidal (Cipolletti)

U 0 = 1.5

Rectangular - suppressed

U 0 = 1.5

Sutro (Proportional)

U 0 = 1

(symmetrical or asymmetrical)

For rated flows under free flow conditions, the head is measured upstream of the weir
plate at a minimum distance of 3 times the maximum head (i.e. where the liquid
surface is not affected by drawdown).

* The transducer must be above the maximum head by at least the
blanking value, P47.

7ML19985AB01 OCM III 54

SIMPLE EXPONENTIAL DEVICES, P3 = 0

KHAFAGI VENTURI

15 cm (6")

plan

transducer *

0

head

front

side

For rated flows under free flow conditions, the hea d is measured 15 cm (6") upstream
from the beginning of the converging section.

* The transducer must be above the maximum head by at least the
blanking value, P47.

7ML19985AB01 OCM III 55

SIMPLE EXPONENTIAL DEVICES, P3 = 0

TYPICAL PARSHALL FLUME

C

2/3 C

plan

transducer *

0

head

front

side

For rated flows under free flow conditions, the head is measured at 2/3 the length of
the converging section upstream of the beginning of the throat section.

* The transducer must be above the maximum head by at least the
blanking value, P47.

7ML19985AB01 OCM III 56

SIMPLE EXPONENTIAL DEVICES, P3 = 0

TYPICAL LEOPOLD LAGCO

throat

Q

converging

point of measurement

plan

side

diverging

transducer *

0

head

front

For rated flows under free flow conditions, the head is measured at a point upstream
referenced to the beginning of the converging section. Refer to the following table.

Flume Size Point of Measurement

(pipe dia. in inches) mm inches

4 - 12 25 1.0

15 32 1.3

18 38 1.5

21 44 1.8

24 51 2.1

30 64 2.5

36 76 3.0

42 89 3.5

48 102 4.0

54 114 4.5

60 127 5.0

66 140 5.5

72 152 6.0

* The transducer must be above the maximum head by at least the
blanking value, P47.

7ML19985AB01 OCM III 57

BS-3680 Rectangular Flume, P3 = 1

‘U’ parameters required * ‘U’ parameters calculated **

U0 = approach width B U4 = Cv

U1 = throat width b U5 = Cd

U2 = hump height p U6 = A

U3 = throat length L

*obtain from manufacturer’s specifications.

**

calculated by OCM -3. May be viewed by accessing ‘U’ parameter.

Reference

ABSOLUTE CALCULATION, P4 = 0¤

For flows that can be calculated by the equation:

q = (2/3)

0.5

x g

x Cv x Cs x Cd x B x h

1.5

1.5

where : q = flow rate Cv = velocity coefficient

b = throat width Cs = shape coefficient

g = gravitational acceleration Cd = discharge coefficient

h = head

RATIOMETRIC CALCULATION, P4 = 1¤

For flows that can be calculated by the equation:

q = q

x Cd/Cd

cal

x Cv/Cv

cal

x (h/h

cal

cal

1.5

)

where : q = flow rate

q

= flow rate at maximum head

cal

h = head

h

= maximum head

cal

Cv = velocity coefficient

Cv

= velocity coefficient for maximum head

cal

Cd = discharge coefficient for head

Cd

= discharge coefficient for maximum head

cal

¤

Refer to Operation \ Flow Calculation.

7ML19985AB01 OCM III 58

BS-3680 RECTANGULAR FLUME

0
head

3 to 4 x h

h

max

transducer *

p

L

* The transducer must be above the maximum head by at least the
blanking value, P47.

7ML19985AB01 OCM III 59

BS-3680 Round Nose Horizontal Crest Weir, P3 = 2

‘U’ parameters required * ‘U’ parameters calculated **

U0 = crest width b U3 = Cv

U1 = crest height p U4 = Cd

U2 = crest length L U5 = A

*

obtain from manufacturer’s specifications.

**

calculated by OCM -3. May be viewed by accessing ‘U’ parameter.

Reference

ABSOLUTE CALCULATION, P4 = 0¤

For flows that can be calculated by the equation:

1.5

q = (2/3)

0.5

x g

x Cv x Cs x Cd x b x h

1.5

where : q = flow rate Cv = velocity coefficient

g = gravitational acceleration Cs = shape coefficient

b = throat width Cd = discharge coefficient

h = head

RATIOMETRIC CALCULATION, P4 = 1¤

For flows that can be calculated by the equation:

q = q

x Cd/Cd

cal

x Cv/Cv

cal

x (h/h

cal

cal

1.5

)

where : q = flow rate

q

= flow rate at maximum head

cal

h = head

h

= maximum head

cal

Cv = velocity coefficient

Cv

= velocity coefficient for maximum head

cal

Cd = discharge coefficient for head

Cd

= discharge coefficient for maximum head

cal

¤

Refer to Operation \ Flow Calculation.

7ML19985AB01 OCM III 60

BS-3680 ROUND NOSE HORIZONTAL CREST WEIR

transducer *

3 to 4 x h

max

* The transducer must be above the maximum head by at least the
blanking value, P47.

7ML19985AB01 OCM III 61

BS-3680 TRAPEZOIDAL FLUME, P3 = 3

‘U’ parameters required * ‘U’ parameters calculated **

U0 = approach width B U5 = Cv

U1 = throat width b U6 = Cd

U2 = hump height p U7 = Cs

U3 = throat length L U8 = A

U4 = slope m

*obtain from manufacturer’s specifications.

**

calculated by OCM -3. May be viewed by accessing ‘U’ parameter.

Reference

ABSOLUTE CALCULATION, P4 = 0¤

For flows that can be calculated by the equation:

q = (2/3)

0.5

x g

x Cv x Cs x Cd x b x h

1.5

1.5

where : q = flow rate Cv = velocity coefficient

g = gravitational acceleration Cs = shape coefficient

b = throat width Cd = discharge coefficient

h = head

RATIOMETRIC CALCULATION, P4 = 1¤

For flows that can be calculated by the equation:

q = q

x Cs/Cs

cal

x Cd/Cdal x Cv/Cv

cal

x (h/h

cal

cal

1.5

)

where :

q = flow rate Cs

q

= flow rate at maximum head Cv = velocity coefficient

cal

h = head Cv

h

= maximum head Cd = discharge coefficient for head

cal

Cs = shape coefficient for head Cd

= shape coefficient for maximum head

cal

= velocity coefficient for maximum head

cal

= discharge coefficient for maximum head

cal

¤

Refer to Operation \ Flow Calculation.

7ML19985AB01 OCM III 62

BS-3680 TRAPEZOIDAL FLUME

p

b

end

B

transducer *

3 to 4 x h

max

plan

L

h

* The transducer must be above the maximum head by at least the
blanking value, P47.

7ML19985AB01 OCM III 63

p

side

BS-3680 U-Flume, P3 = 4

‘U’ parameters required * ‘U’ parameters calculated **

U0 = approach diameter Da U4 = Cv

U1 = throat diameter D U5 = Cd

U2 = hump height p U6 = Cu

U3 = throat length L U7 = A

*

obtain from manufacturer’s specifications.

**

calculated by OCM -3. May be viewed by accessing ‘U’ parameter.

Reference

ABSOLUTE CALCULATION, P4 = 0¤

For flows that can be calculated by the equation:

q = (2/3)

0.5

x g

x Cv x Cu x Cd x D x h

1.5

1.5

where : q = flow rate Cv = velocity coefficient

g = gravitational acceleration Cu = shape coefficient

b = throat width Cd = discharge coefficient

h = head

RATIOMETRIC CALCULATION, P4 = 1¤

For flows that can be calculated by the equation:

q = q

x Cu/Cu

cal

x Cd/Cd

cal

x Cv/Cv

cal

x (h/h

cal

cal

1.5

)

where : q = flow rate

q

= flow rate at maximum head

cal

h = head
h

= maximum head

cal

Cu = shape coefficient for head
Cu

= shape coefficient for maximum head

cal

Cv = velocity coefficient
Cv

= velocity coefficient for maximum head

cal

Cd = discharge coefficient for head
Cd

= discharge coefficient for maximum head

cal

¤

Refer to Operation \ Flow Calculation.

7ML19985AB01 OCM III 64

BS-3680 U-FLUME

0

head

3 to 4 x h

Da

h

max

transducer *

p

L

D

* The transducer must be above the maximum head by at least the
blanking value, P47.

7ML19985AB01 OCM III 65

BS-3680 FINITE CREST WEIR, P3 = 5

‘U’ parameters required * ‘U’ parameters calculated **

U0 = crest width b U3 = C

U1 = crest height p U4 = Cp

U2 = crest length L

*

obtain from manufacturer’s specifications.

**

calculated by OCM -3. May be viewed by accessing ‘U’ parameter.

Reference

ABSOLUTE CALCULATION, P4 = 0¤

For flows that can be calculated by the equation:

q = (2/3)

0.5

x g

x C x Cp x b x h

1.5

1.5

where : q = flow rate C = a function of h and L

g = gravitational acceleration
b = crest width Cp = a correction factor as a function
h = head of h and p applied to C

RATIOMETRIC CALCULATION, P4 = 1¤

For flows that can be calculated by the equation:

q = q

x C/C

cal

x Cp/Cp

cal

x (h/h

cal

cal

1.5

)

where : q = flow rate

q

= flow rate at maximum head

cal

h = head

h

= maximum head

cal

C = discharge coefficient for head

C

= discharge coefficient for maximum head

cal

Cp = correction fa ctor for C

Cp

= correction factor for C

cal

cal

¤

Refer to Operation \ Flow Calculation.

7ML19985AB01 OCM III 66

BS-3680 FINITE CREST WEIR

transducer *

3 to 4 x h

max

* The transducer must be above the maximum head by at least the
blanking value, P47.

7ML19985AB01 OCM III 67

BS-3680 THIN PLATE RECTANGULAR WEIR, P3 = 6

‘U’ parameters required * ‘U’ parameters calculated **

U0 = approach width B U3 = Ce

U1 = crest width b U4 = K

b

U2 = crest height p

*obtain from manufacturer’s specifications.

**

calculated by OCM -3. May be viewed by accessing ‘U’ parameter.

Reference

ABSOLUTE CALCULATION, P4 = 0¤

For flows that can be calculated by the equation:

q

= Ce x

2

√⎯⎯⎯2g x be x (

⁄

3

where : q = flow rate Ce = a function of h, p, b and B

g = gravitational acceleration be = effective crest width (b + K

b = crest width h

h = head K

1.5

h

)

e

= effective head (h + Kh)

e

= 1 mm

h

)

b

RATIOMETRIC CALCULATION, P4 = 1¤

For flows that can be calculated by the equation:

q = q

x Ce/Ce

cal

x (h/h

cal

cal

1.5

)

where : q = flow rate

q

= flow rate at maximum head

cal

h = head

h

= maximum head

cal

Ce = discharge coefficient for head

Cv

= discharge coefficient for maximum head

cal

¤

Refer to Operation \ Flow Calculation.

7ML19985AB01 OCM III 68

BS-3680 THIN PLATE RECTANGULAR WEIR

transducer *

4 to 5 x h

max

* The transducer must be above the maximum head by at least the
blanking value, P47.

7ML19985AB01 OCM III 69

BS-3680 THIN PLATE V-NOTCH WEIR, P3 = 7

‘U’ parameters required * ‘U’ parameters calculated **

U0 = notch angle alpha U1 = Ce

*

obtain from manufacturer’s specifications.

**

calculated by OCM -3. May be viewed by accessing ‘U’ parameter.

Reference

ABSOLUTE CALCULATION, P4 = 0¤

For flows that can be calculated by the equation:

0.5

q = Ce x 8/15 x tan(

/2) x (2g)

α

where : q = flow rate h = head

x h

2.5

g = gravitational acceleration Ce = function of h and

= notch angle alpha

α

◊

angle is restricted to 90°, 53.133° or 28.066°. Otherwise use ratiometric calculation.

RATIOMETRIC CALCULATION, P4 = 1¤

◊

α

For flows that can be calculated by the equation:

q = q

x Ce/Ce

cal

x (h/h

cal

cal

2.5

)

where : q = flow rate

q

= flow rate at maximum head

cal

h = head

h

= maximum head

cal

Ce = discharge coefficient for head

Ce

= discharge coefficient for maximum head

cal

¤

Refer to Operation \ Flow Calculation.

7ML19985AB01 OCM III 70

BS-3680 THIN PLATE V-NOTCH WEIR

transducer *

4 to 5 x h

max

* The transducer must be above the maximum head by at least the
blanking value, P47.

7ML19985AB01 OCM III 71

RECTANGULAR WEIR (CONTRACTED), P3 = 8

‘U’ parameters required *

U0 = crest width b

*

obtain from manufacturer’s specifications.

**

calculated by OCM -3. May be viewed by accessing ‘U’ parameter.

Reference

ABSOLUTE CALCULATION, P4 = 0¤

For flows that can be calculated by the equation:

q = K x (b - 0.2h) x h

1.5

where : q = flow rate

h = head

K = constant

RATIOMETRIC CALCULATION, P4 = 1¤

For flows that can be calculated by the equation:

q = q

x (b - 0.2h)/(b - 0.2h

cal

) x (h/h

cal

cal

2.5

)

where : q = flow rate

q

= flow rate at maximum head

cal

h = head

h

= maximum head

cal

¤

Refer to Operation \ Flow Calculation.

7ML19985AB01 OCM III 72

RECTANGULAR WEIR - CONTRACTED

transducer *

4 to 5 x h

max

* The transducer must be above the maximum head by at least the
blanking value, P47.

7ML19985AB01 OCM III 73

ROUND PIPE, P3 = 9

(based on the Manning Formula)

‘U’ parameters required *

U0 = pipe inside diameter D

U1 = slope (fall/run) s

U2 = roughness coefficientn

*obtain from manufacturer’s specifications.

Reference

ABSOLUTE CALCULATION, P4 = 0¤

For flows that can be calculated by the equation:

q = K/n x f(h) x s

0.5

where : q = flow rate

h = head

K = constant

f(h) = A x R

0.66

A = cross sectional area

R = hydraulic radius

s = slope of hydraulic gradient

n = roughness coe fficient

RATIOMETRIC CALCULATION, P4 = 1¤

For flows that can be calculated by the equation:

q = q

x f(h)/f(h

cal

cal

)

where : q = flow rate h = head

q

= flow rate at maximum head h

cal

= maximum head

cal

¤

Refer to Operation \ Flow Calculation.

7ML19985AB01 OCM III 74

ROUND PIPE

transducer

*

**

* This dimension should be at least 15 cm (6") shorter than
the blanking value, P47.

** The transducer must be above the maximum head by at least the
blanking value, P47.

h

7ML19985AB01 OCM III 75

PALMER-BOWLUS FLUME *, P3 = 10

‘U’ parameters required **

U0 = maximum flume width, h

*

typically those manufactured by Warminster or Plasti-Fab.

**

obtain from manufacturer’s specifications.

max

Reference

RATIOMETRIC CALCULATION, P4 = 1¤

For flows that can be calculated by the equation:

q = q

x f(h/h

cal

max)

/ f(h

cal/hmax

)

where : q = flow rate

q

= flow rate at maximum head

cal

h = head

h

= maximum head

cal

f(h/h

) is determined by polynomial synthesis

max

¤

Refer to Operation \ Flow Calculation.

7ML19985AB01 OCM III 76

PALMER-BOWLUS FLUME

D / 2, point of measurement *

D = pipe or sewer diameter

* for rated flows under free flow conditions

transducer **

0

head

** The transducer must be above the maximum head by at least the
blanking value, P47.

7ML19985AB01 OCM III 77

H-FLUME *, P3 = 11

‘U’ parameters required *

U0 = maximum listed head, h

*

as developed by the U.S. Department of Agriculture, Soil Conservation Service.

**

obtain from manufacturer’s specifications.

max

Reference

RATIOMETRIC CALCULATION, P4 = 1¤

For flows that can be calculated by the equation:

q = q

x f(h/h

cal

max

)/f(h

cal/hmax

)

where : q = flow rate

q

= flow rate at maximum head

cal

f(h/h

¤

Refer to Operation \ Flow Calculation.

) and f(h

max

cal/hmax

) are determined by polynomial synthesis

7ML19985AB01 OCM III 78

H-FLUME

transducer *

point of measurement

plan

front

side

For rated flows under free flow conditions, the head is measured at a point downstream
from the flume entrance. Refer to the following table.

Flume Size Point of Measurement

D (feet) cm inches

0.5 4.7 1.88

0.75 6.7 2.69

1.0 9.1 3.63

1.5 13.5 5.38

2.0 17.9 7.19

2.5 22.5 9.00

3.0 27.2 10.88

4.5 40.5 16.19

* The transducer must be above the maximum head by at least the
blanking value, P47.

7ML19985AB01 OCM III 79

UNIVERSAL HEAD vs FLOW, P3 = 12

The flow curve is characterized by entering the head (A

) and flow (A

even

odd

)
ordinates for the number of data points (n, 4 to 16) over the flow range. The first
point (A0,A1) generally being at 0 head and the last point (A

2n-2,A2n-1

) generally being

at maximum head .

‘U’ parameters required *

U0 = number of data points

= head

A

even

A

= flow rate

odd

*

obtain from manufacturer’s specifications.

Reference

RATIOMETRIC CALCULATION, P4 = 1¤

(n, 4 to 16)

For flows that can be calculated by the equation:

q = q

where : f(h) and f(h

¤

x f(h)/f(h

cal

cal

)

) are polynomials based on interpolation of data points

cal

Refer to Operation \ Flow Calculation.

7ML19985AB01 OCM III 80

UNIVERSAL HEAD vs FLOW

e. g. typical compound weir

Parameters

U0 = 11

A0 = 0 head, point 1 A12 = 1.05 head, point 7

A1 = 0 flow, point 1 A13 = 2.65 flow, point 7

A2 = 0.3 head, point 2 A14 = 1.2 head, point 8

A3 = 0.1 flow, point 2 A15 = 3.4 flow, point 8

A4 = 0.6 head, point 3 A16 = 1.4 head, point 9

A5 = 0.7 flow, point 3 A17 = 5.0 flow, point 9

A6 = 0.8 head, point 4 A18 = 1.7 head, point 10

A7 = 1.5 flow, point 4 A19 = 8.0 flow, point 10

A8 = 0.95 head, point 5 A20 = 2 head, point 11

A9 = 2.25 flow, point 5 A21 = 11.8 flow, point 11

A10 = 1 head, point 6

A11 = 2.5 flow, point 6

odd

A

F

l
o
w

R
a

t
e

For best accuracy concentrate data points where changes in flow rate are the greatest.

7ML19985AB01 OCM III 81

Head

A

even

RECTANGULAR AREA X VELOCITY, P3 = 13

‘U’ parameters required * ‘U’ parameters calculated **

U0 = channel width B U1 = area (h)

*obtain from manufacturer’s specifications.

**

calculated by OCM -3. May be viewed by accessing ‘U’ parameter.

Reference

ABSOLUTE CALCULATION, P4 = 0¤

For flows that can be calculated by the equation:

q = 1/1000 x B x h x V

where : q = flow rate in l/sec

B = channel width in cm

h = head in cm

V = velocity in cm/sec

RATIOMETRIC CALCULATION, P4 = 1¤

For flows that can be calculated by the equation:

q = q

x A/A

cal

cal

x v/v

cal

where : q = flow rate

q

= flow rate at maximum head

cal

h = head

h

= maximum head

cal

v = ve locity

v

= velocity at maximum head

cal

¤

Refer to Operation \ Flow Calculation.

7ML19985AB01 OCM III 82

RECTANGULAR AREA X VELOCITY

transducer *

* The transducer must be above the maximum head by at least the
blanking value, P47.

7ML19985AB01 OCM III 83

TRAPEZOIDAL AREA X VELOCITY, P3 = 14

‘U’ parameters required * ‘U’ parameters calculated **

U0 = channel top width B U3 = area (h)

U1 = channel base width b

U2 = channel depth ht

*

obtain from manufacturer’s specifications.

**

calculated by OCM -3. May be viewed by accessing ‘U’ parameter.

Reference

ABSOLUTE CALCULATION, P4 = 0¤

For flows that can be calculated by the equation:

q = 1/1000 x (b + mh) x v

m = (B - b)/d

where : q = flow rate, l/sec

B = channel top width, cm
b = channel bottom width, cm
d = depth of channel, cm
h = head, cm
v = flow velocity, cm/sec

RATIOMETRIC CALCULATION, P4 = 1¤

For flows that can be calculated by the equation:

q = q

x A/A

cal

cal

x v/v

cal

A = (b + mh) x h

A

= (b + mh

cal

cal

) x h

cal

m = (B - b)/d

where : q = flow rate, l/sec

B = channel top width, cm
b = channel bottom width, cm
d = depth of channel, cm
h = head, cm
v = flow velocity, cm/sec

¤

Refer to Operation \ Flow Calculation.

7ML19985AB01 OCM III 84

TRAPEZOIDAL AREA X VELOCITY

transducer *

* The transducer must be above the maximum head by at least the
blanking value, P47.

7ML19985AB01 OCM III 85

MODIFIED TRAPEZOIDAL AREA X VELOCITY, P3 = 15

‘U’ parameters listed * ‘U’ parameters calculated **

U0 = channel top width B U3 = area (h)

U1 = channel base width b

U2 = transition height ht

*obtain from manufacturer’s specifications.

**

calculated by OCM -3. May be viewed by accessing ‘U’ parameter.

Reference

ABSOLUTE CALCULATION, P4 = 0¤

For flows that can be calculated by the equation:

q = 1/1000 x (b + mh) x v for h ≤ d

q = 1/1000 x ((b + md)d + (B(h - d))) x v for h ≥ d

m = (B - b)/d

where : q = flow rate, l/s d = height of transition, cm

B = channel top width, cm h = head, cm
b = channel base width, cm v = flow velocity, cm/sec

RATIOMETRIC CALCULATION, P4 = 1¤

For flows that can be calculated by the equation:

q = q

x A/A

cal

cal

x v/v

cal

for h ≤ d: A = (b + mh) x h

A

= (b + mh

cal

cal

) x h

cal

for h ≥ d: A = (b + md) x d + B(h - d)

A

= (b + md) x d + B(h

cal

cal

- d)

m = (B - b)/d

where : q = flow rate d = depth of channel

q

= flow rate at h

cal

cal

h = head
B = channel top width, cm v = flow velocity, cm/sec
b = channel base width, cm

¤

Refer to Operation \ Flow Calculation.

7ML19985AB01 OCM III 86

MODIFIED TRAPEZOIDAL AREA X VELOCITY

transducer *

* The transducer must be above the maximum head by at least the
blanking value, P47.

7ML19985AB01 OCM III 87

U-CHANNEL AREA X VELOCITY, P3 = 16

‘U’ parameters required * ‘U’ parameters calculated **

U0 = base diameter D U1 = area (h)

*

obtain from manufacturer’s specifications.

**

calculated by OCM -3. May be viewed by accessing ‘U’ parameter.

7ML19985AB01 OCM III 88

U-CHANNEL AREA x VELOCITY

transducer *

* The transducer must be above the maximum head by at least the
blanking value, P47.

7ML19985AB01 OCM III 89

CIRCULAR AREA X VELOCITY, P3 = 17

‘U’ parameters listed * ‘U’ parameters calculated **

U0 = conduit diameter ID U1 = area (h)

*

obtain from manufacturer’s specifications.

**

calculated by OCM -3. May be viewed by accessing ‘U’ parameter.

7ML19985AB01 OCM III 90

CIRCULAR AREA X VELOCITY

transducer

*

**

h

* This dimension should be at least 15 cm (6") shorter than
the blanking value, P47.

** The transducer must be above the maximum head by at least the
blanking value, P47.

7ML19985AB01 OCM III 91

GULL-WING AREA X VELOCITY, P3 = 18

‘U’ parameters required * ‘U’ parameters calculated **

U0 = channel base width b U4 = area (h)

U1 = lower angle alpha (α)

U2 = upper angle beta (β)

U3 = transition height ht

*

obtain from manufacturer’s specifications.

**

calculated by OCM -3. May be viewed by accessing ‘U’ parameter.

7ML19985AB01 OCM III 92

GULL WING AREA X VELOCITY

transducer *

* The transducer must be above the maximum head by at least the
blanking value, P47.

7ML19985AB01 OCM III 93

V

EGG-SHAPED AREA X VELOCITY, P3 = 19

‘U’ parameters listed * ‘U’ parameters calculated **

U0 = top radius R U3 = area (h)

U1 = bottom radius r

U2 = axial displacement d

*

obtain from manufacturer’s specifications.

**

calculated by OCM -3. May be viewed by accessing ‘U’ parameter.

Reference

ABSOLUTE CALCULATION, P4 = 0¤

For flows that can be calculated by the equation:

q = 1/1000 x A x v

where : q = flow rate in l/sec

v = flow velocity in cm/sec

RATIOMETRIC CALCULATION, P4 = 1¤

For flows that can be calculated by the equation:

q = q

x A/A

cal

cal

x v/v

cal

where : q = flow rate

q

= flow rate at h

cal

cal

A = cross sectional area of flow
A

= cross sectional area of flow at h

cal

v = flow velocity

¤

Refer to Operation \ Flow Calculation.

cal

7ML19985AB01 OCM III 94

EGG-SHAPED AREA X VELOCITY

transducer *

standpipe **

* This dimension should be at least 15 cm (6") shorter than
the blanking value, P47.

** The transducer must be above the maximum head by at least the
blanking value, P47.

7ML19985AB01 OCM III 95

UNIVERSAL AREA X VELOCITY, P3 = 20

Arbitrary area is typically used when the primary element and/or its flow do not fit any
of the primary elements covered by P3. There is no user difference between absolute
and ratiometric calculations P4.

The flow curve is characterized by entering the head (A

) and area (A

even

odd

)
ordinates for the number of data points (n, 4 to 16) over the flow range. The first
point (A0,A1) generally being at 0 head and the last point (A

2n-2,A2n-1

) generally being

at maximum head .

‘U’ parameters required * ‘U’ parameters calculated **

U0 = number of data points

A

= head

even

A

= area

odd

*

obtain from manufacturer’s specifications.

**

calculated by OCM -3. May be viewed by accessing ‘U’ parameter.

e.g. typical open channel

(n, 4 to 16)

U1 = area (h)

transducer *

* The transducer must be above the maximum head by at least the
blanking value, P47.

7ML19985AB01 OCM III 96

UNIVERSAL AREA X VELOCITY

odd

A

Area

U0 = 8

A0 = 0 head, point 1

A1 = 0.0 area, point 1

A2 = 0.05 head, point 2

A3 = 0.03 area, point 2

A4 = 0.1 head, point 3

A5 = 0.06 area, point 3

A6 = 0.15 head, point 4

A7 = 0.09 area, point 4

A8 = 0.25 head, point 5

A9 = 0.18 area, point 5

A10 = 0.45 head, point 6

A11 = 0.35 area, point 6

A8 = 0.70 head, point 7

A9 = 0.59 area, point 7

A8 = 1.00 head, point 8

A9 = 0.89 area, point 8

Head

A

even

For best accuracy concentrate data points where changes in flow are the greatest.

7ML19985AB01 OCM III 97

7ML19985AB01 OCM III 98

MAINTENANCE

The OCM-3 requires very little maintenance due to its solid-state circuitry. However, a
program of periodic preventative maintenance should be initiated. This should include
regula r inspection, general cleaning, overall system performance checks and standard
good housekeeping practices.

A periodic inspection of the transducer is recommended, at which time any build-up of
material on the face should be removed.

The enclosure should be cleaned using a vacuum cleane r and a clean, dry brush.

For battery replacement refer to Installation / Installing the Memory Back-up Battery.

7ML19985AB01 OCM III 99

Error Code Listing

1 number underflow

2 number overflow

3 divide error

4 bad argument

5 invalid parameter

6 system is locked

7 head exceeds BS-3680 spec

ERROR CODES

8 must use ratiometric

9 invalid angle size

10 invalid selection

11 value is view-only

12 characterizer in use

13 feature not available

14 need whole number

15 invalid date

16 invalid time

20 can’t zero auxiliary device

21 b must be greater than R-r

7ML19985AB01 OCM III 100

COMMUNICATIONS

The OCM-3 provides serial communication either through Milltronics proprietary
bipolar current loop or industry standard RS-232. Communication can be used to
provide a video or paper printout of OCM activity. It can also be used to provide
remote programming and retrieval of the data log, from devices such as computers
and PLCs.

When using the bipolar current loop, communication runs of up to 1,500 m can be
achieved, as opposed to the limited runs of 15 m using RS-232. By terminating the
bipolar current loop with a Milltronics CVCC, the communication format is then
converted to RS-232.

OCM - 3
site number
(P39 )

RS-232

serial printer

customer’s
computer *

bipolar current loop

CVCC **

customer’s
computer *

optional parallel printer

* Milltronics OCM -3 Utilities Software available

** provides conversion to RS -232 or 422

7ML19985AB01 OCM III 101