The HM35 digital pressure gauge is a pressure-measuring instrument with an integrated
pressure sensor for the measurement of differential, relative or absolute pressures and
vacuum. Its versatile range of functions and high precision render it suitable for a wide
range of applications. Via the infrared interface (IR) and SCPI (Standard Commands for
Programmable Instruments) commands, the HM35 can communicate with a PC. Its
operation is very simple, and supports the user in his measurement tasks.
Operating modes
• Pressure measurement / Differential pressure
• Min./Max. values
• Mean value (average)
• Pressure change rate
• Data logging
Selectable configuration possibilities
• Data logging
Æ Interval time, print/transfer, deleted memory
• Configuration
Æ Measurement units, display filter, auto. switch-off time, auto zero, lighting level, etc.
• Average period (period for determining average value)
• Date and Time (real-time clock)
• Calibration
Æ Date of last calibration date, manual recalibration
2 Safety information
•The pressure values and overload levels stated on the rating plate and quoted in
these operating instructions must not be exceeded, as otherwise the pressure sensor could be destroyed or there could be a risk of injury.
•Only use pressure hoses with a maximum loading capacity corresponding to that
necessary for the application.
•Ensure that the pneumatic hoses are securely fitted! Do not use damaged or kinked
hoses.
• Do not open up the instrument (this would void the guarantee).
• The instrument must be stored within the permissible storage temperature range.
The instrument must not be put into operation in an
explosive environment!
Wear eye protection if working with pressures > 1bar!
3
3 Operation
3.1 Switching on and off
Switching on Briefly press the On/Off key () (< 1 s)
For precise measurements, the HM35 must first be switched on for at
least 1 minute (warm-up phase).
Switching off Briefly press the On/Off key
or
automatic switch-off 3, 10 or 60 minutes after the last time key operation
(automatic switch-off does not take place during Average, Change Rate
and Data Logging measurements or in IR
Notes
• The HM35 switches on automatically when the supply voltage is connected.
• The HM35 continues to work in battery mode following an interruption of the supply
voltage
•In case of a change in temperature, the HM35 must be allowed to adapt to the new
ambient temperature for a least 30 minutes while switched off in order to attain the
best measurement accuracy.
• The day/time, battery level and accuracy will be briefly displayed at switch on:
• After switch-on, the HM35 switches to the last operational mode used, e.g.:
() (< 1 s),
and network operation).
• With the display filter activated, wait until the transient effect finishes (approx. 5 s).
4
3.2 Lighting
Switching on Press the On/Off-key
() for > 1 s
Brightness control In the Menu, select the Configuration → Lighting function and
select an adjustment of Off, Level 1, Level 2 or Level 3.
Switching off Briefly press the On/Off key
() (< 1 s)
(switch off the instrument),
or automatic switch-off after 20 s.
With mains operation, the HM35 must be switched off manually.
3.3 Pneumatic connection
Designation Pressure range
Hose 4/6 mm
NPT1/8“ internal 10 ... 90 bar
Plug in nipple „Rectus“ Type 20
M10 x 1 internal thread (for „Minimess“ connector) all
≤ 7,5 bar
≤ 30 bar
Ensure that the pneumatic hoses are connected correctly!
+P Higher pressure
S- Lower pressure (not available with the absolute and relative pressure version)
When screwing onto a coupling, it is important to hold the
coupling steady with a wrench to prevent any turning!
Never secure by holding the casing itself!
5
3.4 Functions and operating modes
Key clear hold
Functions
PRESSURE
DIFFERENCE
▲ MIN/MAX Sets Max/Min to
▼ AVERAGE 4)
CHANGE RATE 5)
DATA LOGGING
Zero: sets
measured value to
3)
zero
current measured
value
Sets measured
value to zero
3)
Freezes all
current
measurement
values
--
To Menu selection
1)
Stop/Menu
Start 2)
--
Starts measuring
Starts data
logging
Notes
1) Once a measurement procedure has been started, the menu selection is blocked.
2) During a measurement procedure (after Start has been pressed), you can switch
between functions. This permits, for example, the observation of the Min/Max
function during data logging.
3) The Clear key has no function in the absolute pressure instruments.
4) The AVERAGE function creates an arithmetic average value of all measured values
during the time period selected in the menu. After expiry of the time period, the
average value will be displayed.
5) Measurement of the leak rate (diff/gauge sensor) or tendency (abs. sensor). The
pressure change (CHANGE RATE) from the start time to the current time will be
displayed. The first display occurs 10 s after the start.
3.5 Menu selection and set-up
Navigation within the Menu selection
clear
▲▼
Brief (< 1 s) 1 level back
Long (> 1 s) Back to the function level/operating modes
Selection of Set-up/Functions
The functions shown inverted on the display will be carried out if the Function key
) is pressed.
(
The currently selected setting for values is marked with '9'. In the following table, the
default values are correspondingly marked (factory settings).
6
Key
Data logging
Interval Interval period
manual
25 M./s
10 M./s
1 s 9 2 s
5 s
10 s
30 s
1 min
2 min
5 min
10 min
30 min
1 h
3 h
6 h
12 h
24 h user Set with ▲/▼/ EDIT/OK
▲ Print Data Logging
▼ Press 'Start' Print/send via IR
Clear Memory
Press 'Clear' Deletes the data memory
Configuration
Pressure Unit 9 mbar
bar
Pa
hPa
kPa
MPa
kg/cm2
kg/m2
mmHg
cmHg
mHg
inHg
mmH2O
cmH2O
mH2O
inH2O
ftH2O
psi
lb/in2
lb/ft
torr atm
2
Notes
7 8
Key
Display Filter Filters the display values 1)
9 On Off
Auto-Off Auto. switch-off
3 min 9 10 min
60 min
Auto-Zero
On Sensor auto-zeros at switch-on
9 Off
Beep Warning beeper
9 On
Off
Lighting Off Level 1 Only Level 1 possible for Ex-models
Level 2
▲ 9 Level 3
▼ IR Interface
9On At switch-on, the automatic
Off Automatic connection is de-activated
Average period Time period for average value
10 s
30 s
1 min
2 min 9 5 min
10 min
30 min
1 h
3 h
6 h
12 h
24 h user Set with ▲/▼/EDIT/OK
Date & Time dd.mm.yyyy Set with ▲/▼/ EDIT/OKhh:mm:ss Set with ▲/▼/ EDIT/OK
Calibration
History Displays the last calibration date
Manual re-calibration Manual re-calibration of the zero
Notes
if measured value < 1% FS
connection to the PC is activated for
2 minutes
point and limit value
Note
1) With the filter function active, short-term measurement variations should be
suppressed, resulting in a steadier display. Measured values via the interface and in
the Data Logging Memory will not be filtered.
3.6 Data logging
3.6.1 Data recording
Every time that the Data Logging is started, an information header ("Header") will first be
saved: The measured values will then be saved sequentially. "Stop" will be saved after
every interruption of the logging or if manual storage is carried out. At the end of all the
data loggings, "End" will be saved. Measured values can be uniquely identified by their
header.
Designation Example 1 Data Logging Type of Data 2)
Date
Time 12:00:00
Interval 30 s
Function PRESS
Unit mbar
01.01.2001
1000.0
1001.1
1001.5
1000.3
999.7
Stop
End
INTEGER
Header
DISCRETE
1)
Measurement series
DISCRETE
DISCRETE
FLOAT
Designation Example 2 Manual saving Type of Data 2)
Date 01.01.2001
Time 12:00:00
Interval Manual
Function PRESS
Unit inHg
Date 01.01.2001
Time 12:00:33
Interval Manual
Function PRESS
Unit inHg
Date 01.01.2001
Time 12:01:45
Interval Manual
Function PRESS
Unit inHg
End
29.92 1st measured value 1)
Stop
29.29 2nd measured value 1)
Stop
28.00 3rd measured value 1)
Stop
Header 1st measurement
DISCRETE
Header 2nd measurement
DISCRETE
Header 3rd measurement
DISCRETE
DISCRETE
INTEGER
DISCRETE
FLOAT
INTEGER
DISCRETE
FLOAT
INTEGER
DISCRETE
FLOAT
9
Notes
1) „Over“ (data type DISCRETE) for invalid pressure value
2) For the Data Type key, refer to the table on Page 18.
3) User-interval period will, for example, be displayed as follows, “user 01:15:00”
3.6.2 Transfer of data to a PC
(with HM35 Communication Software)
1. Install the IR (IrDA) -adapter according the instructions of the manufacturer.
2. Install the HM35 Communication Software.
3. Start the HM35 Communication Software.
4. Place the instrument max. 20 cm from the IR (IrDA)-Adapter and switch it on. Ensure
a line-of sight connection between instrument and IR-adapter!
If there is no communication with the instrument for more than 2 minutes, the IR
interface of the instrument turns off automatically! By restarting the instrument the IR
interface is reactivated.
3.6.3 Deleting data
1. In the Menu, select the Data Logging → Clear Memory function.
2. Press the Clear key.
3.7 Communication
3.7.1 IR/RS232-Protocol
COM-Port Settings
Baudrate 9600
Data bits 8
Parity no
Protocol no
Stop bit 1
S Y S T : T i m e SP 0 7 , 0 8 , 0 9 HT * 2 5 5 CR (with checksum)
S Y S T : T i m e SP 0 7 , 0 8 , 0 9 HT CR (without checksum)
Reading the time:
S Y S T : T i m e ? HT * 1 4 2 CR (with checksum)
S Y S T : T i m e ? HT CR (without checksum)
Response from instrument to PC
<Return Value 1> [ , <Return Value 2> ] [ , <Return Value 3> ] [ , ...] HT * <CS> CR
SCPI Command: SCPI command according the table on following pages
CS: Checksum
Return Value: Response from instrument
[ ] Option
ASCII-character Hex-Code Meaning
SP 0x20 Space
HT 0x09 Horizontal Tabulation
CR 0x0D Carriage Return
* 0x2A Asterisk
, 0x2C comma
SCPI Commands
There is no difference between small and capital letters.
Checksum (CS)
The use of the checksum is optional. A * indicates a following checksum. The ASCIIcharacter * is included in the calculation of the checksum. The checksum is calculated
from the low byte.
Example:
Reading the date
S Y S T : D a t e ? HT *
53 59 53 54 3A 44 61 74 65 3F 09 2A
83 89 83 84 58 68 97 116 101 63 09 42
hex
dez
sum: 37D
893
low byte: 7D
hex
125
dez
hex
dez
The checksum is 125 decimal.
Command:
S Y S T : D a t e ? HT * 1 2 5 CR (with checksum)
S Y S T : D a t e ? HT CR (without checksum)
11
Return Value
Command processed:
Return Value = o k
Example for response: o k HT * 1 3 CR
Error
Return Value Meaning
er-001 RS232 Protocol checksum Error
er-110 Header Error; Too short
Header Error; Too many subnodes
Header Error; Query not at leaf node
Header Error; Multiple querys
Header Error; Characters after query
Header Error; Too long
er-113 Undefined Header; Undefined command
er-109 Missing parameter
Missing parameter; Boolean expected
Missing parameter; String expected
Missing parameter; Discrete expected
Missing parameter; Not of expected type
er-101 Invalid character; Terminator expected
er-108 Invalid parameter; Out of bounds
Invalid parameter; Too long
er-203 Command Protected
er-999 EEProm Read/Write Error
er-002 Fatal Command Execution Error
Example: Checksum Error
Response: e r – 0 0 1 HT * 200 CR
--- <hh>,<mm>,<ss> INTEGER Query time hh: hours, mm: minutes
--- <Error_number>,
--- <version> FLOAT SCPI query and firm-
ON, OFF --- --- Beeper enable / disable
--- --- Input date yyyy: year,
"<Error_description>
(;<Devicedependent info>)"
INTEGER,
STRING
pressure value
temperature
Query SCPI Error Queue STRING with ‚fixed text‘
ware version
Individual value
°C, individual value
mm: month
dd: day
dd: day
ss: seconds
ss: seconds
and optional ‚free text’,
separated by a semicolon,
maximum 255 digits
e.g. '2001.0' , ‘FW:300’
--- <value> INTEGER Query battery state Range 0...100, value in %
--- <range> STRING
--- <tolerance> STRING Query sensor tolerance e.g. '0.05 %FS'
--- <type, MOD, S/N> STRING Query instrument
ON, OFF --- --- Set filter for display
--- --- --- Zero measure pressure
Query sensor
measurement range
in mbar
identification
value (ZERO)
e.g. "1,000 mbar“
e.g. "HM3500DLH200,
MOD00A,1234567“
15
Command Sub-node 1 Sub-node 2 Transfer parameter Parameter data type
SYSTem :SET :AOFF <time> DISCRETE
:OFF --- ---
:AZERo <state> BOOLEAN
:INTerval <interval> DISCRETE
:AVERage <interval> DISCRETE
:CONFig :IRDA <status> BOOLEAN
DIAGnostic
DISPlay
MEMory :COPY :DLOG? --- ---
:ERRors? --- ---
:BRIGhtness <level> DISCRETE
:DELete :ALL --- ---
*CLS
*IDN?
*STB?
*TST?
*RST
--- ---
--- ---
--- ---
--- ---
--- ---
16
Parameter
enu
limits
3min, 10min, 60min --- --- Set auto Off time
--- --- --- Switch off instrument
ON, OFF --- --- Enable/disable auto zero
Feedback data
Feedback data
type
Description Remarks
25M./s, 10M./s,
1s ... 24h
10s, 30s ... 24h --- --- Set time period for
OFF --- --- Set auto IrDA connection
--- <err>,<err>,<err>... INTEGER Query the BIT-Error
<message> DISCRETE Query the BIT-error
OFF, level 1,
level 2, level 3
--- <data> diverse Select Memory Data
--- --- --- Delete Memory Data
--- --- --- Delete Status and Error
--- <type, MOD, S/N> STRING Query instrument
--- <data> INTEGER Query Status Byte
--- --- Set interval time for Data
Logging
Average
memory
memory
--- --- Brightness setting for
LCD backlight
Logging (cyclic)
Logging
Memory
identification
Similar to Menu
Similar to Menu
Variable amount of
Feedback data, err: 0...255
If Error memory deleted:
'No Errors!’
EX-instrument only OFF
and Level 1, similar to
M
Complete reading,
Format: see 3.6.1
See SYST:IDENT?
--- <data> INTEGER Initiate a Self-Test
--- --- --- Reset command
17
Data Type Key
Designation Description Example
INTEGER Decimal number, whole numbers only 123
FLOAT Floating-point number 123.45
I-FLOAT Floating-point number, transferred as an INTEGER.
This means that it will not be transferred in the floating-point
format, but as an INTEGER – value coded according to the IEEE754 standard.
DISCRETE Discrete values, do not use “ in the text, similar to Menu selection mbar
BOOLEAN Boolean values: ON or OFF (similar to DISCRETE) ON
STRING Character string "ABCDE“
3242721280
(corresponds to -12.5)
Notes regarding control commands
• Cyclical commands Commands that last longer are processed cyclically. They will be automatically interrupted if a command occurs
that requires an output.
• " (Inverted commas) A STRING is identified by inverted commas and a full-stop. These must be transferred with it (unlike DISCRETE).
• ' (apostrophe) An apostrophe is used, for example for emphasis. The apostrophe itself will not be transferred.
• ( ) (brackets) Parameter inside round brackets are optional The brackets themselves will not be transferred.
• , (comma) The comma is used to separate arguments. The next argument must follow immediately after the comma
(no SPACE, ASCII-Code 32
dez
).
18
3.8 Battery replacement
• Open the battery compartment and insert 3 x 1,5 V Mignon cell AA, IEC LR6.
Always replace all three batteries at the same time!
Ensure correct polarity!
3.9 Calibration
Re-calibration may only be carried out by specialist staff and with the corresponding
pressure standards.
We recommend that you have the HM35 re-calibrated at least once a year, and, in case
of highest demands for precision, several times a year.
Manual re-calibration
• In the Menu, select the Calibration→Manual Calibration function.
Zero point (Offset)
1. Open the pressure connection or, with the absolute pressure unit, set the given
2. Press the Function key (
Î the zero point will be re-calibrated.
Dispose of used batteries in accordance with environmental
regulations
pressure value to the normal pressure.
!
)
Full-scale value
1. Set the given pressure value to the normal pressure.
2. Press the Function key (
Î the full-scale value will be calibrated and the HM35 returns to normal operation.
)
19
Notes
• The calibration is always carried out in mbar.
• The calibration must take place at a stable room temperature of 22 °C ± 2 °C.
• A calibration value will only be accepted if it lies within ± 5 % of the full-scale
value of the HM35.
• With the pressure connections open, it is possible to only re-calibrate the zero point.
• The date of the last calibration will be stored in the Calibration History.
• In case of manual re-calibration, the previous measurement will become invalid.
You should always carry out a complete accuracy check afterwards.
4 Specifications
4.1 Technical data
Measuring media Instrument air or inert gases
Media-compatibility all media that is compatible with stainless steel 18/8
(DIN 1.4305)
Linearity, hysterisis and according to measuring range and use
repeatability accuracy See Table 4.2
Units according to measuring range and use
See Table 4.3
Operating temperature 0 °C to 50 °C
Storage temperature -20 °C to 60 °C
Humidity max. 95 % rH. (non-condensing)
Case protection IP 54
Power supply • 3 x 1,5 V Mignon-cell AA, IEC LR6 or accumulator
The HM35 requires no maintenance. It can be cleaned with a damp cloth. Do not use
cleaning agents containing solvents!
See the relevant chapters for battery replacement und re-calibration.
During longer storage, remove the batteries from the instrument.
Do not drop below or exceed the admissible storage temperatures of -20 °C to 60 °C!
6 Warning messages and faults
Code Fault / Display Possible cause Correction
Does not switch on Power supply missing Possibly replace the batteries.
Battery possibly inserted incorrectly.
Possibly plug in power supply
correctly.
Instrument inaccurate
No change of the measured
14
13
06
04
15
07
05
No IR communication
value
PRESSURE
OUT OF RANGE!
PRESSURE
OUT OF RANGE!
TEMPERATURE
OUT OF RANGE!
TEMPERATURE
OUT OF RANGE!
REF. VOLTAGE
FAILURE!
NOT CALIBRATED! Incorrect calibration of the
LOW BATTERY! Battery voltage too low Replace batteries
• Re-calibration carried out
inaccurately
• Not zeroed
• Natural aging of the pressure
sensor
Excess pressure on sensor Send instrument to the manufacturer
Measurement range has been
exceeded by more than 10 %.
• Excess pressure on sensor
• Electrical fault
Pressure sensor exposed to
temperature outside permissible
range (< -5 °C or > 55 °C)
Used outside permissible
temperature range
Internal reference voltage error Send instrument to the manufacturer
instrument
• Line-of-sight connection
interrupted
• Separation too large
• PC-configuration
• Re-calibrate
• Vent and press Zero
• Have it re-calibrated
for repair.
Set up the permissible measurement
pressure.
Send instrument to the manufacturer
for repair.
Observe permissible operating
temperature and temperature of the
medium.
Observe permissible operating
temperature.
for repair.
Send instrument to the manufacturer
for repair.
• Re-establish line-of-sight
connection
• Max. distance 50 cm
• Check IR connection
24
7 Accessories
Standard 3 x 1,5 V batteries IEC LR6
Operating instructions
SCS Test certificate
Options 6V mains supply unit 100 - 240 V, 50 - 60 Hz, 1,15 A
Leather case with carrying strap
Service-Set (transport case)
Hand pump
Infrared RS232 serial adapter
NPT 1/8" adapter
„Rectus“ adapter, type 20
Communication software for MS-Windows® (95/98, 2000, XP)
8 Summary of technical characteristics
Characteristics HM35 Remarks
Basic functions
1 pressure sensor installed
Absolute pressure
Differential pressure
Relative pressure
Vacuum (relative under-pressure)
for inert gases
Media compatibility rel./abs.
Measuring ranges / Accuracy See separate table
Calibrated temperature range 0 ... 50 °C
Measuring functions
Pressure / Differential pressure
Min/Max
Average
Change Rate
Other functions
Set-up/Configuration
Unit switchable
Display filter
Auto-off
Record interval
Average period
Display rate 2 M/s
Max. measurement rate 25 M/sApprox..
Date / Time (real time)
Analogue bar display
Real time data logging
Data logging / manual record
Print record
Number of records 10742 Max.
Zeros with key
Automatic zeroing
Hold
Display accuracy at start-up
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
The instrument is only calibrated
in the over-pressure range
Average per time period
Tendency / leak rate
Free choice
Free choice
25
Characteristics HM35 Remarks
Low battery display
Acoustic signal
Self-test
Housing
Hand-held
Splash proof IP54
Connections
Tube 4/6 mm
NPT1/8“ internal
Plug-in nipple „Rectus“ Type 20
M10 x 1 internal thread
Power supply socket