Dwyer Instruments HM28D3H30000, HM28D3H10000, HM28D3F30000, HM28D3F10000, HM28D3C30000 User manual

Operating instructions
Digital handheld
pressure gauge

HM28

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Contents

1 Description....................................... 4

2 Safety details ...................................4

3 Operating .........................................4

3.1 Switching on and off ........................4

3.2 Pneumatic connection .....................4

3.3 Operating modes .............................4

3.4 Configuration ...................................6

3.5 RS 232 mode ................................... 7

3.6 Battery change ..............................10

3.7 Recalibration.................................. 10

4 Specifications ................................ 10

4.1 Technical data ............................... 10

4.2 Measuring ranges ..........................12

4.3 Mains supply unit connection ........12

5 Maintenance ..................................12

6 Warning messages and faults ....... 13

7 Accessories ...................................13

8 Calibration instructions ..................14

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Operating instructions

ON = On
OFF = Off
MODE = Select operating mode

- Pressure measurement

- Min./Max.

- Leak rate

- Datalogging
CLEAR/ZERO = Zero setting
PRINT/HOLD = Print and freeze display
START/STOP = Data recording / printing
SET = Select config. modes
SELECT = Select config. data

c Matrix display
d Connection for pneumatic hoses
e Connection for plug-in power supply unit
f Connection for RS 232 interface

d

c

e

f

Important!

Please note warning symbol
in the operating instructions.

Copyright (c) by LOVE CONTROLS.
The contents of this publication may not be
copied without the express permission of
LOVE CONTROLS.
Subject to dimension and design changes.

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3

1 Description

The „LOVE CONTROLS“ handheld pressure
gauge HM28 is a digital pressure measuring
instrument with integrated pressure sensor
for the measurement of differential, relative or
absolute pressures and vacuum. Its versatile
range of functions and high precision makes
it suitable for a wide range of applications.

Configuration possibilities:

• Autom. switching off, selectable time

• Selectable resolution and damping

• Selectable units of time

• Selectable measurement units

• General reset to standard setting

• Selectable data transfer rate

• Configuration printout

• Selectable measuring intervals

2 Safety details

Switching off Press the OFF key, or auto-

matic switching off 1,10 or 60

min after the last keystroke.
In case of a temperature change the instrument
requires at least 30 minutes to adjust to the
new ambient temperature.

3.2 Pneumatic connection

For measuring ranges up to 7000 mbar, 4/6
mm or NPT 1/8" connectors can be connected
depending on model. Higher ranges are
equipped with NPT 1/8".

Ensure correct connection of the pneumatic
hoses!

+P high pressure
S- low pressure (not available

with the absolute and relative
pressure version)

The pressure values stated on the rating plate
and mentioned in these operating instructions
must not be exceeded otherwise the pressure
sensor can be destroyed.

Do not use the instrument in danger
zones (explosives zones)!
Wear eye protection for pres­sures > 1bar!

3 Operating

3.1 Switching on and off

Switching on Press the ON key (the maxi-

mum permissible measuring
range and the class appears
on the display).
For precision measurements
the instrument must be switch­ed on for at least 1 minute
(warm-up phase).

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Measuring negative differential or relative
pressures:

connect “S-”
or

change ports “S-“ and “+P”.

The HM28 will display a positive value.

3.3 Operating modes

The modes in the matrix below can be selected
in succession by pressing the MODE key.

After switching ON, the instrument is always
in the mode „normal“.

4

Î negative pressure,

When screwing on a coupling it
is important to hold with a span­ner in the opposite direction.
Never hold at case only!

Switching on

Normal
(differential)
and
analogue/hold

Normal
(absolute)
and differential

Zoom

Min/Max

Leak rate

Tendency
(absolute)

Record 1)

Print Record

print
hold

print

print

print

print

print

start/stop

print

quick keystroke:
max. output speed

Keystroke
approx.1s:
single or fast
output start/stop
printing

zero

display

zero

diff

zero

display

zero

(reset)

zero

display

clear

memory

Display example

Max. Range:

200 mbar

Full scale error

0.05 %

123.45 mbar
====== or
HLD 123.4 mbar

1013.2 mbar

DIF 1013.2 mbar

123.45

MAX 150.0 mbar
MIN 100.0 mbar

1234.5 mbar

LEK 2.1 /min

1013.2 mbar

TND - 15.7 /min
REC 432.1 mbar

STOP 30 s MEM 1
REC 432.1 mbar

RUN 30 s MEM 321

432.1 mbar
STOP 30 s MEM 901

PRINT RECORD
PUSH PRINT

PRT 432.1 mbar
321 00:13:30

PRT
Record stopped

Notes

Measuring range
displayed in desired
unit

Accuracy class as a %
of full scale reading

Only with differential
or relative pressure
models

Hold, store indicated
value

Only with absolute
pressure mode Zero

sets Diff to 0
Measurement in large

figures
With absolute pressure,

reset to actual value

Only with Diff./Rel.

(unit/time unit)

Only with absolute
pressure (unit/time unit)

If measurement
memory cleared

Recording runs up to
964 values

Recording stopped

Appears only if values
are stored

Printing / display with
time

Recording stopped

1) at 70 bar the measurements are stored in [bar]

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3.4 Configuration

Select mode:
Press >2 seconds

Store and exit:
Press >2 seconds

Î on the display appears

CONFIGURATION

Î on the display appears

SAVE CONFIGURATION

set unit mbar, kPa, bar, 2)

mmH2O, mH2O,
mmHg, psi, inH2O,
inHg, hPa, Pa, MPa

set high
resolution1) low

set damping off

on

set baudrate 9600, 4800, 2400,

1200

set auto-off 1, 10, 60 min
continuous continue

set time unit minutes
hours hours

set 1, 5, 10, 20, 30, 60 s
Rec. interval 2, 3, 5, 10, 30, 60 min

1) manual, off

set 2.5 Hz (400 ms)
display rate 5 Hz (200 ms)

Display example

UNIT
mbar

RESOLUTION Display resolution,
high influences measuring rate

in RS 232 mode

DAMPING 90% recovery after 4
off measurements (when ON)

BAUDRATE
9600

AUTO OFF Automatic switching off or
10 min continuous mode

TIME UNIT For leak rate, tendency
minutes

REC INTERVAL Off = record mode is
5 s (1.3h) deactivated

(max. record interval)

DISPLAY RATE Normal mode indication/zoom

2.5 Hz (400 ms) (influences DAMPING)

Notes

general reset? set on default values zero

print print now
configuration?

1) If changed, the measurement memory is cleared 2) See in 4.1 "Technical data"

GENERAL RESET? Reset all settings and clear
PUSH ZERO measurement memory

GENERAL RESET? After actuating ZERO
RESET OK

PRINT CONFIG? Unit, ...
PUSH PRINT

PRINT CONFIG? After actuating PRINT
PRINTING

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3.5 RS 232 mode

The HM28 can be remotely operated from a
personal computer via an RS 232 interface.
The automatic switching off (chapter 3.1) is
inactive. Connection by means of a RS232­cable.

Plug pin assignment RS 232, DB 9 (female)

The answer is terminated with a CR

- The checksum is formed from the least
significant byte of the command string

Code-decoding of control command

«readconfig»

Pin Assignment Pin Assignment
1 DCD 6 DSR
2 TXD 7 RTS
3 RXD 8 CTS
4 DTR 9 SHIELD
5 GND

Protocol

ASCII-commands
9600/4800/2400/1200 baud, 8 bit, no parity,
1 stop bit,
XON/XOFF - protocol (17 dec/19 dec)

Notes

- The HM28 is switched on when the
supply voltage is applied

- The HM28 sends "XON" every 3 seconds
To determine the baud rate, read-in
"XON" in each transfer rate until "XON"
is correctly identified

- To go to remote control mode, interrogate
"XON", immediately send the "remote"
command and then read-in the
acknowledgement "ok"

- Only lower case letters are accepted

- Observe > 0,1 s delay before the next
command after "setbaud" command

- To acknowledge the answer of the HM28
without reading it back, just send a "XON"

- The symbol "*" followed by the checksum
must be suffixed to each string. The string
must be terminated with a CR

- A "TAB" is prefixed to each answer of the
HM28, a "*" suffixed and the checksum
sent.

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Code Configuration

Pressure unitPressure unit

Pressure unit

Pressure unitPressure unit

5 MPa(7-70bar)
6 Pa(25mbar-7bar)
7 kPa
8 bar
9 mH2O(with 70bar,

otherwise mmH2O)

10 mmHg(not with

70bar)
11 psi
12 inH2O
13 inHg (not with

70bar)
14 hPa
15 mbar

ResolutionResolution

Resolution

ResolutionResolution

0 low
1 high

DampingDamping

Damping

DampingDamping

0on
1 off

BaudrateBaudrate

Baudrate

BaudrateBaudrate

0 1200 Baud
1 2400 Baud
2 4800 Baud
3 9600 Baud

Code Configuration

Switch. off timeSwitch. off time

Switch. off time

Switch. off timeSwitch. off time

0 60 min
1 continous
2 1 min
3 10 min

Time unitTime unit

Time unit

Time unitTime unit

0 /hours
1 /minutes

Storage intervalStorage interval

Storage interval

Storage intervalStorage interval

2 10 s
3 20 s
4 30 s
5 60 s
6 2 min
7 3 min
8 5 min
9 10 min
10 30 min
11 60 min
12 manual
13 off
14 1 s
15 5 s

Display rateDisplay rate

Display rate

Display rateDisplay rate

0 5 Hz
1 2.5 Hz

Reply to control command «readconfig»

A whole number is returned as a reply

msb lsb

#### #### #### ####
|||| |||| |||| ****- Pressure unit
|||| |||| |||*------ Resolution
|||| |||| ||*------- Damping
|||| |||| **-------- Baudrate
|||| ||**----------- Switching off time
|||| |*------------- Time unit
|***-*-------------- Storage interval
*------------------- Display rate

7

block keypad

"RESOLUTION high" output10 M/s

"RESOLUTION low" output 20 M/s

following send "XON"

(full=ok, empty=change)

(tab)[record_stopped] * 200 CR Recording is stopped

(tab)[out_of_range] * 164 CR Measurement out of range

(tab)[record_end] * 0 CR Recording stopped (waits at "XON"

and sends back "ok" )

±4°C (±39 °F)

change to keypad

Control commands/syntax Answer from HM28/syntax Description

remote * 182 CR (tab)[ok] * 13 CR Switch to remote control and

local * 53 CR (tab)[ok] * 13 CR Switch to keypad

off * 101 CR (tab)[ok] * 13 CR Switch off instrument

readpress * 243 CR (tab)"Value" _ "Unit" * Checksum CR Interrogate measurement

readpressfast * 161 CR (tab)"Value" * Checksum CR (tab)"Value" * Checksum CR Fast measurement interrogation

$ (tab)[ok] * 13 CR Exit "readpressfast" mode

readrange * 211 CR (tab)"Range" _ "Unit" * Checksum CR Interrogate measuring range

readbat * 253 CR (tab)"full"/"empty" * 230/98 CR Interrogate battery capacity (lobat)

readrecord * 69 CR (tab)"Recinterval" _ (tab)"Value" _ (tab)"Value" _ (tab)"Value" Interrogate stored measured

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readtemp * 124 CR (tab)"Value" _ °C * Checksum CR Interrogate internal temperature,

clearmem * 112 CR (tab)[ok] * 13 CR Clear datalogging memory

readconfig * 60 CR (tab)Code (see decoding in table page 17) * Checksum CR Readout actual configuration

setzero * 54 CR (tab)[ok] * 13 CR Zero indication

setdefault * 91 CR (tab)[ok] * 13 CR Reset all settings and clear memory,

setunit_kpa * 146 CR (tab)[ok] * 13 CR Corresponding units

setunit_mbar * 248 see 4.1 Technical data

setunit_bar * 139

low: 20 M/s

off at RS232 mode

periodically (default value)

Control commands/syntax Answer from HM28/syntax Description

setunit_mmh2o * 57

setunit_mmhg * 255

setunit_psi * 162

setunit_inh2o * 54

setunit_inhg * 252

setunit_hpa * 143

setunit_pa * 39

setunit_mpa * 148

setbaud_9600 * 1 CR (tab)[ok] * 13 CR Select baud rate (answer with

setbaud_4800 * 254 new baud rate, wait >0,1s

setbaud_2400 * 248 before "XON")

setbaud_1200 * 245

resolution_high * 62 CR (tab)[ok] * 13 CR Select measurement resolution

resolution_low * 240 and indication, high:10 M/s,

settempmode_0 * 33 CR (tab)[ok] * 13 CR Temp. measuring will be switched

settempmode_1 * 34 Temp. measuring will be done

setrecint_off * 86 CR (tab)ok * 13 CR Select storage interval (secondes)

setrecint_man * 87 (tab)ok

setrecint_1 * 76 (tab)ok

setrecint_5 * 80 (tab)ok

setrecint_10 * 124 (tab)ok

setrecint_20 * 125 (tab)ok

setrecint_30 * 126 (tab)ok

setrecint_60 * 129 (tab)ok

setrecint_2m * 186 (tab)ok Select storage interval (minutes)

setrecint_3m * 187 (tab)ok

setrecint_5m * 189 (tab)ok

setrecint_10m * 233 (tab)ok

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3.6 Battery change

- Open battery receptacle

- Insert 9 V-alkali battery (IEC 6LR61) or
accumulator

Ensure correct polarity!

Correct disposel of the used
batteries according to environment
regulations!

3.7 Recalibration

Recalibration to be carried out by specially
skilled staff only.

Relevant instructions see in section 8. We
recommend to recalibrate the instrument at
least once a year.

4 Specifications

Control commands/syntax Answer from HM28/syntax Description

setrecint_30m * 235 CR (tab)ok * 13 CR

setrecint_60m * 238 (tab)ok

setautooff_man * 198 CR (tab)ok * 13 CR Select autom. switching off time (minutes)

setautooff_1 * 187 (tab)ok

setautooff_10 * 235 (tab)ok

4.1 Technical data

Measuring media instrument air or

Media-compatible all media compatible
types with stainless steel

(tab)[er] * 10 CR Error

setautooff_60 * 240 (tab)ok

setdamp_off * 115 CR (tab)ok * 13 CR Damping off

setdamp_on * 21 (tab)ok Damping on

setdisrate_2.5 * 23 CR (tab)ok * 13 CR Set display rate (Hz)

setdisrate_5 * 183 (tab)ok

setunit_perh * 5 CR (tab)ok * 13 CR Tendency .../h

setunit_permin * 225 (tab)ok Tendency .../min

Note: The character _ indicates a space

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inert gases

18/8 (DIN 1.4305)

Units Measuring ranges

up to 7 bar 10 to 30 bar 70 bar

mbar x x x
bar x x x
Pa x - ­kPa x x x
hPa x x ­MPa - x x
mmH

Ox x -

2

mH

O- -x

2

mmHg x x ­psi x x x
inH

Ox xx

2

inHg x x -

Linearity, hysteresis and
repeatability
(10 °C to 35 °C) ± 0,2 % F.S.
(50 °F to 95 °F) (standard) ± 1 digit

± 0,1 % F.S.
(option) ± 1 digit
± 0,05 % F.S.
(option) ± 1 digit
(according to
measuring range)

Operating temperature -5 °C to 50 °C

(23 °F to 122 °F)

Storage temperature -20 °C to 60 °C

(-4 °F to 140 °F)
Humidity 30 to 95 % rH
Case protection class IP 54
Power supply 9 V-battery (IEC

6LR61) or

accumulator

regulated plug-in

mains supply unit

(7 to 14 VDC)
Current consumption <9 mA
Operating time (battery) appr. 70 h
Baud rate RS232 9600/4800/2400/

1200 baud

Measuring rate in RS232- mode

-Class 0,2 20 measurements/s

-Class 0,1 and 0,05 10 measurements/s
Measuring rate, 2 ½ or
normal mode 5 measurements/s
Memory capacity max. 964

measurements

Memory interval manual,

1,5,10,20,30,60 s
2,3,5,10,30,60 min

Display LCD matrix,

2 lines of 16
characters

Pneum. ports hose 4/6 mm or

NPT 1/8"
Case dimensions 152x83x34/29 mm
Weight incl. battery 270 g

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4.2 Measuring ranges

Metric Range English Range Max. load capacity Max. static pressure

(rounded)

0 ... 2.5 kPa 0 ... 10 inH2O 12.5 kPa 50 inH2O 700 kPa 100 psid
0 ... 7 kPa 0 ... 28 inH2O 35 kPa 140 inH2O 700 kPa 100 psid
0 ... 20 kPa 0 ... 80 inH2O 150 kPa 600 inH2O 700 kPa 100 psid
0 ... 30 kPa 0 ... 120 inH2O 150 kPa 600 inH2O 700 kPa 100 psid
0 ... 50 kPa 0 ... 200 inH2O 400 kPa 1600 inH2O 700 kPa 100 psid
0 ... 100 kPa 0 ... 14.5 psid/g 400 kPa 58 psid/g 700 kPa 100 psid
0 ... 110 kPa 0 ... 15.9 psia 400 kPa 58 psia -- -­0 ... 200 kPa 0 ... 29 psia/d/g 700 kPa 100 psia/d/g 700 kPa 100 psid
0 ... 700 kPa 0 ... 100 psia/d/g 1700 kPa 245 psia/d/g 1700 kPa 245 psid
0 ... 1000 kPa 0 ... 145 psid/g 2700 kPa 390 psid/g 2700 kPa 390 psid
0 ... 1700 kPa 0 ... 245 psid/g 2700 kPa 390 psid/g 2700 kPa 390 psid
0 ... 3000 kPa 0 ... 435 psig 7000 kPa 1000 psig -- -­0 ... 7000 kPa 0 ... 1000 psig 14000 kPa 2000 psig -- --

a = absolute pressure
d = differential pressure
g = relative pressure

Conversion factors
1 mbar = 0,1 kPa
1 mbar = 0,0010 bar

1 mbar = 10,20 mmH
1 mbar = 0,7501 mmHg
1 mbar = 0,0145 psi
1 mbar = 0,4015 inH
1 mbar = 0,02953 inHg
1 mbar = 1,0 hPa

The maximum load capacity applies for

))

)

))

relative overpressure and negative
pressure. The instrument is calibrated

from 0 to100% of the measuring
range. Exceeding or underrunning this

range by up to about 10% is still
displayed.

Differential pressure sensors (d)

))

)

))

doesn’t measure the same value on
the P and S side mandatorily because
of her geometry.

O

2

O

2

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4.3 Power supply unit connection

The HM28 can be operated by a regulated
plug-in power supply unit.

Input 115V, 60 Hz
Output 9 V DC ± 20 %, 100 mA

(7 to 14 V DC)

5 Maintenance

The HM28 requires no maintenance. It can be
cleaned with a damp cloth. Do not use cleaning
agents containing solvents!
See the relevant chapters for battery change
and recalibration.

12

6 Warning messages and faults

Fault/indication Possible cause Remedy

ERROR
OUT OF RANGE

CHANGE BATTERY

No change in
measurement

Does not switch on

Instrument
inaccurate

10% exceeding or under­running of measuring range

Battery voltage too low

Over pressure applied to
pressuresensor

No power supply

Inaccurate recalibration

Not zeroed

Natural aging of the pressure
sensor

7 Accessories

Standard 1 9 V block battery

1 operating instructions

Option Plug-in power supply unit

115V, 60Hz
Leather case with carrying strap
Service set
Hand pump with variobellows5bar
Handpump 20 bar
SCS test certificate
Adapter RS232 9M-25F
Adapter NPT1/8"
Communication SW package

comprising:

- RS232-IF cable (9 pole fem.)

- Communication-software for
MS Windows

- Measurement places
management software for
MS Windows

Apply permissible measuring
pressure

Insert new battery

Dispatch instrument for repair

Fit new battery as required
Battery possibly not correctly inserted
Plug in power supply unit correctly

Repeat recalibration

Vent and actuate zero

Carry out recalibration

13

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8 Calibration instructions

Recalibration to be carried out by
specially skilled staff only!

Actuate the following key combinations:

• First press MODE and keep it
pressed

• Next and additionally, press CLEAR/
ZERO and keep pressed until
CALIBRATION is displayed

Exit from this mode is possible at any time via
MODE or OFF.

The instrument must be in operation for at
least 30 minutes (warm up stabilization time).

New calibration values are only stored
when all five setpoints have been
running through correctly and

Calibration at 22 °C (71,6 °F) environmental temperature

An incorrect internal instrument tempera­ture can lead to accuracy fluctuations!

The pressure set points have to be set in
[mbar]!

Check the instrument accuracy after
recalibration!

acceptable values acquired. In the
event of a maloperation, the calibration
process is interrupted and the previous
calibration data are retained.

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LOVE CONTROLS Division
Dwyer Instruments, Inc.
Highway 212 AT 12
Michigan City, IN 46360
USA
Phone ++1 219 879 8868
Fax ++1 219 872 9057

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I-HM28/0501, Art. Nr. 70 792 146 Printed in Switzerland