VPInstruments VPFlowScope In-line 3/8" User manual

VPFlowScope In-line 3/8"
VPINSTRUMENTS.COM
User manual
© 2021 VPInstruments
MAN-VP-VP38-EN-2100 Date: 25-01-2021

All ri ghts res erved. No pa rts of this document may be reproduced in any form or by a ny mea ns - graphi c,
electronic, or mecha ni cal, incl uding photocopying, recording, ta ping, or informa ti on storage a nd retrieval
systems - wi thout the wri tten permi ss ion of the publi s her.
Products that a re referred to i n thi s document ma y be ei ther trademarks and/or regi s tered trademarks of the
res pective owners . The publis her a nd the a uthor make no cl a i m to thes e trademarks.
While every precaution ha s been taken i n the preparation of this document, the publis her a nd the a uthor
as sume no responsi bi l ity for errors or omis s i ons, or for da ma ges res ulti ng from the us e of informa tion
conta i ned in this document or from the us e of programs and source code tha t may a ccompany it. In no event
sha l l the publ is her a nd the a uthor be l i able for a ny loss of profi t or any other commerci a l damage caus ed or
al l eged to have been ca used directly or indirectl y by thi s document.
Crea tion da te: 25-01-2021 in Delft
VPFlowScope In-line 3/8"
© 2021 VPInstruments
Publisher
Van Putten Instruments BV
Buitenwatersloot 335
2614 GS Delft
The Netherlands

3
Table of Contents
1Warning - Read this first 4
2Introduction 5
3Product overview 6
4Quick start 6
5Measurement 7
................................................................................................................................... 7
1 Flow
................................................................................................................................... 7
2 Totalizer
6Mechanical installation 8
................................................................................................................................... 8
1 Installation point
................................................................................................................................... 8
2 Piping table
7Connectivity & communication 10
................................................................................................................................... 10
1 LEDS
................................................................................................................................... 10
2 4 .. 20 mA output
................................................................................................................................... 11
3 Pulse
................................................................................................................................... 12
4 RS485
................................................................................................................................... 12
5 Display
.......................................................................................................................................................... 12
Keypad
8Modbus 13
9Electrical connections 16
................................................................................................................................... 16
1 4 .. 20 mA
................................................................................................................................... 17
2 RS485
10 Specifications 19

© 2021 VPInstruments | MAN-VP-VP38-EN | Revision: 2100 | Date: 25-01-2021
4
1 Warning - Read this first
Compressed gases can be dangerous! Please familiarize yourself with the
forces under pressurized conditions. Respect the local guidelines and
regulations for working with pressurized equipment.
Gas flow through pipes follows certain physical laws. These physical laws
have serious consequences for the installation requirements. Familiarize yourself
with the basic physical laws of flow measurement, to make sure that the product
is installed correctly. Always make sure that upstream length, downstream
length, flow, pressure, temperature and humidity conditions are within
specifications.
Precision instrumentsneed maintenance. Check your flow meter regularly
and make sure it remains clean. When polluted, gently clean the sensor using
de-mineralised water or cleaning alcohol.
Not intended for fiscal metering or billing. Our flow meters are not certified
for fiscal metering. Laws on fiscal metering and billing may vary per country or
state.
Do not overestimate the results. VPInstruments does not take any
responsibility for the correctness of measurement results under field
conditions. The practical measurement uncertainty of a flow meter in the field may
vary, depending on how well it is installed, due to the nature of gas flow. The piping
table provides guidelines on how to optimize the field accuracy. Our products are
not intended to be used as a single means to determine compressor capacity.
Do not open the device. Our instruments are assembled with high precision.
Opening this device is dangerous and may destroy the instrument. Warranty is
voided when you open the instrument.
Feedback leads to product improvement. Please share your experience
with us, as we are continuously improving our products in our commitment to
quality, reliability and ease of use. Let us know via [e-mail]!

© 2021 VPInstruments | MAN-VP-VP38-EN | Revision: 2100 | Date: 25-01-2021
5
2 Introduction
Thank you for purchasing the VPFlowScope In-line 3/8" flow meter. This flow meter is designed to
measure low flow rates of air and oxygen. The built in display will show the actual and total flow and
the Modbus and analog 4..20 mA output enable you to interface with 3rd party monitoring systems.
We have done our best to make this user manual as complete as possible. New users, please read
it carefully to familiarize yourself with our products. Experienced users can check out the Quick start
chapter.
Check the packaging box for any inconsistencies. Should there be any shipping damage, notify the
local carrier. At the same time a report should be submitted to Van Putten Instruments BV,
Buitenwatersloot 335, 2614 GS DELFT, The Netherlands.
This manual is dedicated to:
VPFlowScope In-line 3/8" flow meter

© 2021 VPInstruments | MAN-VP-VP38-EN | Revision: 2100 | Date: 25-01-2021
6
3 Product overview
The VPFlowScope In-line 3/8" is a flow meter which measures flow rates of air and oxygen in 3-8
inch pipes. The actual flow rate and the total flow will be shown on the display in selectable units.
The Modbus and analog 4..20 mA output enables you to interface with 3rd party monitoring systems.
4 Quick start
This chapter contains the basic steps to start using your VPFlowScope In-line 3/8" flow meter.
Additional information on all subjects can be found in the next chapters.
1. Unpack
Unpack the box and check if all items are there and in good shape.
2. Apply power
Connect the unit to a DC power source (14 .. 24 VDC). See chapter 9 Electrical connections for more
information.
3. Mechanical installation
Find the best point of installation for this product. Make sure that the process conditions are within
the specifications of the flow meter and the upstream and downstream straight pipe lengths are
respected.
For installation of the flow meter, the pipe needs to be cut.
Mount the flow meter between the pipe ends using Hylok SICMC-6-6G.
See chapter 6 Mechanical installation for more detailed information.
4. Electrical installation
Connect a cable with 5 Pin M8 connector to the flow meter. The cable can be connected to a central
data acquisition / building management system or data logger via Modbus RTU or 4..20 mA.
Apply 14 .. 24 VDC to power up the device. Use a Class II power supply (less than 2 Amps).
See chapter 9 Electrical connections for more information.
5. Configuration
No configuration is required for proper measurement. Configure the Modbus address or the 4..20 mA
settings when they are used. These settings can be changed in the menu using the buttons.
Optionally the displayed units can be changed. By default they are set to:
Row 1: flow in ln/m
Row 2: total flow in l
Row 3: temperature in °C
It is possible to switch between 1, 2 or 3 parameters.

© 2021 VPInstruments | MAN-VP-VP38-EN | Revision: 2100 | Date: 25-01-2021
7
5 Measurement
For all parameters the update interval is 1 second. Within this second, multiple samples are taken
and averaged to provide a stable and reliable output.
5.1 Flow
The VPFlowScope In-line 3/8" flow meter uses our proprietary insertion type thermal mass flow
sensor. There is no bypass flow, which results in a high robustness and less sensitivity for dirt or
particles. The flow sensor is directly temperature compensated. The flow reading is under normalized
conditions.
The sensor response signal is directly related to
the mass flow rate and can be described by the
following formula:
Vout = k *λ* ρ* v* (Ts-Tg)
Vout = output voltage
k = sensor (geometrical) constant
λ= thermal conductivity of the gas
ρ= density of the gas
v= actual velocity in m / sec
Ts = sensor temperature
Tg = gas temperature
5.2 Totalizer
The totalizer keeps track of the total consumed amount of compressed air in normal cubic meters,
normal liters, normal centiliters or in (M)(M)SCF depending on which unit you choose to read out.
The refresh interval is 1 second. Actual totalizer data will be available on the display and via the
Modbus interface. The totalizer value is written to its internal memory with an interval of 15 minutes.
A power failure may result in maximum 15 minutes of totalizer data loss.
The totalizer can only be reset to zero. It's not possible to set it to any arbitrary value.

© 2021 VPInstruments | MAN-VP-VP38-EN | Revision: 2100 | Date: 25-01-2021
8
6 Mechanical installation
6.1 Installation point
The installation point is crucial for a correct measurement. Sources of error can be: installation
effects, unknown flow profiles, swirls, pressure and temperature effects, humidity effects, oscillations
in the flow, etc. To ensure the highest possible accuracy of flow measurement, the installation and
piping instructions must be followed. Therefore read this paragraph carefully.
Take into account:
Choose a location which is accessible, which allows access for wiring and maintenance activities.
Meet the specifications of the VPFlowScope In-line 3/8" flow meter. When the specifications are
not met, for instance the pressure or temperature level is too high; this will cause inaccurate flow
measurement and can even damage your flow meter.
Do not apply mechanical stress on the VPFlowScope In-line 3/8" flow meter.
Avoid:
Excessive heat, check the temperature specifications
Corrosive atmosphere where possible
Electrical problems (high voltage/ high power)
Mechanical vibration and danger (walking bridges, fork lift trucks)
Any environmental source of potential error
Stop: These devices are only for use with air, oxygen and other non hazardous and non
combustible gases. The maximum working pressure is 10 bar (145 psi)
For compliance with oxygen systems, please strictly follow the safety guidelines as
provided by national laws and/or internal guidelines on use of oxygen equipment.
6.2 Piping table
Check the piping table below and match it for your application. The table shows the amount of
upstream and downstream length depending on the installation. If applicable in front of the meter, use
given upstream length. If applicable behind the meter, use given downstream length. Gas flow in
pipes follows certain rules, which must be observed for optimal measurement results. In some cases
the upstream length needs to be longer, in other cases it can be shorter.
If possible, you can always choose a longer upstream length, as these are minimum
values. The up- and downstream lengths are used industry wide as guidelines, but will
never be a guarantee for obtaining the “true value”.

© 2021 VPInstruments | MAN-VP-VP38-EN | Revision: 2100 | Date: 25-01-2021
9
Piping table
The following table provides a guideline for proper distances between upstream or downstream
objects and the flow meter. The upstream length is the length between the last non-straight object
and the flow meter. If the upstream length is straight, and the distortion is downstream of the flow
meter, you can use the column "downstream length" as a guideline. In very complex situations, with
multiple up- and downstream objects, you should consider another location. This table is a practical
guideline and is not exact science. Practical situations can have multiple sources of distortion,
therefore VPInstruments does not take any responsibility for the correctness.
Picture
Description
Upstream
length2
Downstream
length2
Effect
Single elbow
30 * D1
10 * D1
Distorted flow profile
Complex feed-in
situation (header)
40 * D1
10 * D1
Flow profile will be
distorted
Double elbow, multiple
elbows following each
other
40 * D1
10 * D1
Distorted profile +
swirl
Diameter change from
small to large (gradual or
instant)
40 * D1
5 *D1
Jet shaped flow
Diameter change from
large to small (gradual
change, between 7 and
15 degrees)
10 * D1
5 * D1
Flattened flow profile
1 = inner diameter; 2 = minimumlength

© 2021 VPInstruments | MAN-VP-VP38-EN | Revision: 2100 | Date: 25-01-2021
10
7 Connectivity & communication
The VPFlowScope In-line 3/8" flow meter features two outputs, analog and RS485, which make it
possible to connect to VPVision, a central data acquisition / building management system.
For the analog output there is an option for 4..20 mA or pulse. Which mode is selected affects how
values analog min & max are interpreted.
7.1 LEDS
There are 2 LED's available on the flow meter that indicates the status of the instrument. Various
colors and patterns are available.
Color
Patterns
Descriptions
Green
Blinking at 2 seconds
interval
Initializing during start up
Green
On
Device is on and started up
Orange
Blinking fast
Modbus communication
7.2 4 .. 20 mA output
The 4..20 mA output can be used to connect to VPVision, a central data acquisition / building
management system, a multi-meter or any 4..20 mA based system. The 4..20 mA output is an
active current loop.
There is one 4..20 mA output available. This output can be assigned to one of the measurement
units. The factory default is ln/min.
Scaling is done by setting analog min & analog max using a modbus master tool. Analog min & max
are the numbers represented by 4 mA and 20 mA. The factory default is analog min on 0, analog
max on 50, making 4 mA represent 0 ln/min and 20 mA represent 50 ln/min. Scaling is linear.
Refer to the modbus table in chapter 8 Modbus for register indexes.

© 2021 VPInstruments | MAN-VP-VP38-EN | Revision: 2100 | Date: 25-01-2021
11
Changing analog min & max will not affect the instrument measurement range. Analog out range can
be adjusted to narrow or widen the resolution.
4..20 mA output
Single direction
0%| 100%flow: 4 ma = 0
7.3 Pulse
The VPFlowScope In-line 3/8" flow meter features a low-frequency active pulse output. The pulse is a
‘non potential’ free output as it acts like a controlled current output. To make it passive, an external
isolator can be used.
The pulse output is connected to the internal totalizer value. When the totalizer has increased by the
pulse interval, the pulse will be generated.
When the analog output is in pulse mode, analog min holds the pulse interval, meaning value
represented by a single pulse.
Pulse output

© 2021 VPInstruments | MAN-VP-VP38-EN | Revision: 2100 | Date: 25-01-2021
12
Electrical scheme:
7.4 RS485
RS485 is a serial interface that can be used to connect to VPVision, remote monitoring software or a
building management system. The interface is standardized interface according to standard ANSI/
TIA/EIA-485-A-98.
It is important to match the communication parameters. All devices using this serial interface need to
communicate using the same settings. Various settings are available to match any building
management system.
Communication settings
The RS485 communication settings can be changed with the key pads. Below options are available:
Baud rate: 9600 | 19200 | 38400 | 57600 | 115200
Stop bits: 1 | 2
Parity: None | Even | Odd
Factory default is: 38400, 1, none
The communication protocol is Modbus RTU. More information can be found in chapter 8 Modbus
7.5 Display
The display enables you to read measurement data in real time. In combination with the keypad, it
can also be used to change the most common parameters.
The display provides 1, 2 or 3 rows for real time data. Each row can be configured in the menu by
selecting the desired parameter for this row.
7.5.1 Keypad
The key pad contains 4 buttons to control the flow meter.
Menu / Enter
Used to enter the (sub)menu or to confirm a setting
Escape
Will return from a (sub)menu when not in the data acquisition screen
Button up
Navigate up in the menu
Button down
Navigate down in the menu

© 2021 VPInstruments | MAN-VP-VP38-EN | Revision: 2100 | Date: 25-01-2021
13
8 Modbus
Introduction to Modbus
A complete introduction on the Modbus standard can be found on www.modbus.org. See the
document Modbus_over_serial_line_V1_02.pdf, which can be downloaded from their website. We
strongly recommend to download and read this information carefully before installing Modbus
communication. The following paragraphs in this chapter assume you are familiar with the Modbus
communication standard.
All measurement parameters are available through Modbus in floating point and integer format. The
data will be refreshed every second. Maximum polling interval is 10ms.
The Modbus settings can be changed in the menu using the key pad. Below shows all available
options
Hardware address: 1-247
Integer multiplier: 1-1000
The default settings are hardware address 9 and integer multiplier 10
Data format
Function code 0x03 for reading(Holding register)
Function code 0x06 for writing single register(Holding register)
Function code 0x10 for writing multiple registers(Holding register)
Data format is little-endian word order, big-endian byte order within the word. [CDAB]
Register map
The actual measurement data is placed in holding registers. To read out data, you will need to use
the corresponding holding registers.
Counting starts from 0: register 0 is register index 0 (first) and register 1 is register index 1 (second)
This table starts with register 1 because register 0 is unused.
HEX
Decimal
Description
Type
Read / Write
General information
0001 - 0002
1 - 2
Serial number
32-bit integer
Read
0003 - 0005
3 - 5
Firmware version: major, minor,
patch
3 words
Read
0006 - 0007
6 - 7
Production date
32-bit integer **
Read
Flow
0064 - 0065
100 - 101
Flow range min mn/sec
Floating point
Read
0066 - 0067
102 - 103
Flow range max mn/sec
Floating point
Read
0068 - 0069
104 - 105
Flow mn/sec
Floating point
Read
006A - 006B
106 - 107
Flow sfps
Floating point
Read
006C - 006D
108 - 109
Flow m3n/hr
Floating point
Read
006E - 006F
110 - 111
Flow m3n/min
Floating point
Read
0070 - 0071
112 - 113
Flow m3n/sec
Floating point
Read
0072 - 0073
114 - 115
Flow ln/min
Floating point
Read
0074 - 0075
116 - 117
Flow ln/sec
Floating point
Read
0076 - 0077
118 - 119
Flow SCFM
Floating point
Read

© 2021 VPInstruments | MAN-VP-VP38-EN | Revision: 2100 | Date: 25-01-2021
14
0082 - 0083
130 - 131
Flow mn/sec
32-bit integer
Read
0084 - 0085
132 - 133
Flow sfps
32-bit integer
Read
0086 - 0087
134 - 135
Flow m3n/hr
32-bit integer
Read
0088 - 0089
136 - 137
Flow m3n/min
32-bit integer
Read
008A - 008B
138 - 139
Flow m3n/sec
32-bit integer
Read
008C - 008D
140 - 141
Flow ln/min
32-bit integer
Read
008E - 008F
142 - 143
Flow ln/sec
32-bit integer
Read
0090 - 0091
144 - 145
Flow SCFM
32-bit integer
Read
Temperature
00C8 - 00C9
200 - 201
Temp range min
Floating point
Read
00CA - 00CB
202 - 203
Temp range max
Floating point
Read
00CC - 00CD
204 - 205
Temp celsius
Floating point
Read
00CE - 00CF
206 - 207
Temp fahrenheit
Floating point
Read
00D0 - 00D1
208 - 209
Temp Kelvin
Floating point
Read
00E6 - 00E7
230 - 231
Temp celsius
32-bit integer
Read
00E8 - 00E9
232 - 233
Temp fahrenheit
32-bit integer
Read
00EA - 00EB
234 - 235
Temp Kelvin
32-bit integer
Read
Totalizer
00FA - 00FB
250 - 251
Totalizer m3n
Floating point
Read
00FC - 00FD
252 - 253
Totalizer positive m3n
Floating point
Read
00FE - 00FF
254 - 255
Totalizer negative m3n
Floating point
Read
0100 - 0101
256 - 257
Totalizer MSCF
Floating point
Read
0102 - 0103
258 - 259
Totalizer positive MSCF
Floating point
Read
0104 - 0105
260 - 261
Totalizer negative MSCF
Floating point
Read
0113 - 0114
275 - 276
Totalizer m3n
32-bit integer
Read
0115 - 0116
277 - 278
Totalizer positive m3n
32-bit integer
Read
0117 - 0118
279 - 280
Totalizer negative m3n
32-bit integer
Read
0119 - 011A
281 - 282
Totalizer MSCF
32-bit integer
Read
011B - 011C
283 - 284
Totalizer positive MSCF
32-bit integer
Read
011D - 011E
285 - 286
Totalizer negative MSCF
32-bit integer
Read
Alarm
0130 - 0131
304 - 305
Alarm counter
32-bit integer
Read
0132 - 0132
306 - 306
Alarm status
16-bit integer,
true/false
Read
Alarm/Analog out
0136 - 0137
310 - 311
Analog low boundary **
Floating point
Read / write
0138 - 0139
312 - 313
Analog high boundary **
Floating point
Read / write

© 2021 VPInstruments | MAN-VP-VP38-EN | Revision: 2100 | Date: 25-01-2021
15
Configuration registers
03E8 - 03E8
1000 - 1000
Totalizer reset all
16-bit
Write, any value
03E9 - 03E9
1001 - 1001
Alarm counter reset
16-bit
Write, any value
0422 - 0422
1058 - 1058
Analog output unit
16-bit integer
Read / write
0423 - 0423
1059 - 1059
Analog output mode
16-bit integer
Read / write
044C - 044D
1100 - 1101
Diameter mm
Floating point
Read / write
04B0 - 04B0
1200 - 1200
Modbus address
16-bit integer
Read / write
04B1 - 04B1
1201 - 1201
Modbus multiplier
16-bit integer
Read / write
* Unix epoch time stamp
** Value will only change if both registers are written
Available write operations
Option
Data
Description
4..20 mA
2
3
4
5
6
7
m3n/hr
m3n/min
mn/sec
ln/min
ln/sec
SCFM

© 2021 VPInstruments | MAN-VP-VP38-EN | Revision: 2100 | Date: 25-01-2021
16
9 Electrical connections
NEVER USE AC POWER. THIS WILL VOID WARRANTY AND BRING PERMANENT
DAMAGE TO THE ELECTRONICS. THE INSTRUMENT MIGHT BE DAMAGED
BEYOND REPAIR.
CONNECT THE M8 CONNECTOR BEFORE POWERING UP THE INSTRUMENTS.
The VPFlowScope In-line 3/8" flow meter is equipped with a M8 5-pin connector which contains the
power input, an analogue output and a Modbus interface.
Pin
Signal
Wire color
1
+14 .. 24 VDC
Brown
2
0 Volt
White
3
4..20 mA signal, active
Blue
4
RS485 B
Black
5
RS485 A
Grey
* Wire colors apply to VPInstruments cables
M8 5-pin female connector
Cabling
Shielded twisted pair cabling must be used for proper communication and measurement. Connect
shield to safety ground on one point. The thickness of the wires depends on the cable length. For
cabling below 300 meter | 1000 ft, use 20 awg. For longer runs use 18 awg or better.
Power supply
The input voltage is 14 .. 24 VDC. Make sure that the power supply is at least 14 VDC at the
connector. Voltage drops will occur in long cables resulting in insufficient power. The display will
notify you when there is insufficient power.
9.1 4 .. 20 mA
An advantage of a current loop is that the accuracy of the signal is not affected by voltage drop over
the line. Even if there is significant electrical resistance in the line, the current loop transmitter will
maintain the proper current, up to its maximum voltage capability. The live-zero represented by 4 mA
allows the receiving instrument to detect some failures of the loop. An analogue current loop can be
converted to a voltage input with an external third party precision resistor.
The transmitter output is an active, non- isolated linearized current loop. This means that the + wire
is shared between power supply and the analogue output. A current will draw back from the
instrument to the power supply.
Cabling
3 wires are required to create a current loop. It is advised to use a shielded cable to prevent electrical
noise to affect the signal.
Ohm's law can be used to calculate the maximum distance. There are 2 parameters that needs to be
taken into account.
1. The voltage available is equal to the input voltage
2. The resistance depends on cable quality and length

© 2021 VPInstruments | MAN-VP-VP38-EN | Revision: 2100 | Date: 25-01-2021
17
Example:
Input voltage
24 V
Required maximum current
20 mA
24 V / 0.02 A = 1200 Ohm
1200 Ohm is the maximum load that can be applied with a 24 V input level.
Above example does not include the current consumption of the flow meter itself. When power to the
flow meter is applied using a long cable, include a current consumption of 500mA to the formula.
Electrical scheme
The current meter is placed in between the current output and the power supply ground. You can
also use a digital multimeter to test the current output.
9.2 RS485
Installing a RS485 network require specific knowledge. Not following the specifications
strictly might result in in-correct communications and equipment damage. Please leave
installation up to professional contractors. Make sure that they read this chapter
carefully and follow up all RS485 guidelines.
RS485 is a differential balanced line over twisted pair. It can span relatively large distances up to
1200 meter | 4000 feet. The wires should be connected as a point-to-point configuration, or also
called daisy chain. Do not install as star or ring network! The trunk line goes from the master to all
devices making a drop down to each device. The cable length from the trunk line to the Modbus
device needs to be as small as possible. Junction boxes are used to make the T junction.

© 2021 VPInstruments | MAN-VP-VP38-EN | Revision: 2100 | Date: 25-01-2021
18
Shielded twisted pair should be used. Connection of a third wire between the master and slave
should be done to limit the common mode voltage that can be impressed on the slaves inputs. The
required cable quality depends on the total cable distance, the number of nodes and the
environmental influences. A local contractor can help you select the right cable for your application.
Termination resistor
Termination resistors reduce electrical noise sensitivity. They need to be added to the installation
when cable distances become longer then 10 meter. The value of each termination resistor should be
equal to the cable characteristic impedance (typically, 120 ohms for twisted pairs).
There can only be one termination resistor at the very end of the trunk line. The VPInstruments
junction box features a jumper that can be used to enable a 120 Ohm resistor. When using the
VPInstruments Modbus Junction boxes make sure that the 120 Ohm resistor is only enabled in the
last Modbus Junction box in the daisy chain.
Biasing
When there is no data activity on an RS485 network, the communications lines are "floating" and,
thus susceptible to external noise or interference. Receivers on a RS485 network have built in
hysteresis (200mV differential required to insure known state). To insure that a receiver stays in an
inactive state, when no data signal is present, bias resistors are required. Bias resistors are a pull-up
resistor on Modbus B and a pull-down resistor on the Modbus A line. The value of the bias resistor
depends on the number of devices and the supply voltage. The table below shows which resistor
values can be used for different voltage in a chain with 1 to 8 VPFlowScope M's.
Supply voltage
Bias pull up
Bias pull down
12 V
5 KΩ
1 KΩ
24 V
10 KΩ
1 KΩ
Bus power
The flow meter can be powered via the same trunk line. 2 separate wires are used for power + and
power -. Take in account that long wires with multiple slaves will cause voltage drops. The minimum
supply voltage is 12VDC measured at the last flow meter in the daisy chain.
Electrical scheme

© 2021 VPInstruments | MAN-VP-VP38-EN | Revision: 2100 | Date: 25-01-2021
19
10 Specifications
Please always check the label of your product for the specifications.
Specifications are subject to change as we are continuously improving our products.
Please contact us to obtain the latest specification sheet.
Flow sensor
Measuring principle
Thermabridge™ Thermal Mass Flow sensor
Flow range
2.15 .. 50 ln/min | 0.09 .. 1.77 CFM
Accuracy
5 % of full scale under calibration conditions
Temperature sensitivity
< 1% of measured value per °C
Reference conditions
20 °C, 1000 mbar | 68 °F, 14.50 psi
Gases
Oxygen and compressed air
Gas temperature range
20 .. 32 °C | 68 .. 89.6 °F
Display
Display type
1.8" TFT with auto power save
LED status
LED indicators on all models for power and communication
Outputs
RS485
Modbus RTU
Analogue output
4..20 mA output
Mechanical & Environmental
Dimensions
118 x 42 x 61 mm | 4.6 x 1.7 x 2.4 inch
Weight
400 grams | 14.11 ounces
Material
Brass, polycarbonate
Wetted materials
Brass, Ceramic, Polyurethane, Viton
Protection grade
IP54 | NEMA 3
Ambient temperature
0 .. 50 °C | 32 .. 122 °F
Ambient humidity
0 .. 95 %. Avoid condensation at all times
Pressure rating
PN10
Avoid direct sunlight or radiant heat
Highly corrosive or acid environments should be avoided
Electrical
Supply
14 VDC(*) .. 24 VDC +10% CLASS 2 (UL)
Power consumption
1 Watt (no flow) 3.5 Watt (full flow) +/- 10%
Certification
CE
EN 60950-1, EN 61326-1, EN 61000-3-2, EN 61000-3-3, EN 61326-
1

easy insight into energy flows
MAN-VP-VP38-EN-2100
Date: 25-01-2021
Buitenwatersloot 335
2614 GS Delft
The Netherlands
[e-mail]
www.vpinstruments.com
VPInstruments