Almemo 2190-2 User manual

Operating Instructions
Multimeter
ALMEMO®2190-2
V1.0
31.05.1999
AHLBORN Mess- und Regelungstechnik GmbH
Eichenfeldstraße 1-3 · D-83607 Holzkirchen
Tel. [phone] · Fax [phone]

Operating Instructions
Multimeter
ALMEMO®2190-2
For Reference with the ALMEMO®Manual
Table of Contents
Page
1. INTRODUCTION 4
1.1 Function Range 5
1.2 Operating Controls 7
2. INITIAL OPERATION 8
3. POWER SUPPLY 9
3.1 Operation with Battery and Rechargeable Battery 9
3.2 External Power Supply 10
3.3 Switch On and Off 11
4. CONNECTION OF THE TRANSDUCERS 11
4.1 Transducers 11
4.2 Measuring Inputs and Additional Channels 11
5. DISPLAY 13
6. SENSOR PROGRAMMING 14
6.1 Measuring Range 14
6.2 Dimension 16
2 ALMEMO2190-2
Table of Contents

Page
7. MEASUREMENT 16
7.1 Measured Value and Selection of a Measuring Point 16
7.2 Maximum and Minimum Values 17
7.3 Memory for Momentary Values 18
7.4 Differential Measurement and Correction of Measured Values 18
7.5 Continuous Measuring Point Scan 19
8. TROUBLESHOOTING 20
9. ELECTROMAGNETIC COMPATIBILITY 21
APPENDIX 22
Technical Data 22
Product Overview 22
Your Contacts 23
ALMEMO2190-2 3
Table of Contents

1. INTRODUCTION
The multimeter ALMEMO®2190-2 Version 5 is an instrument from a unique
product range of measuring devices that are all equipped with the ALMEMO®
connector system, which has been patented by Ahlborn GmbH. The intelligent
ALMEMO®connector provides important advantages with regard to the
connection of sensors and peripherals as all parameters are stored in an
EEPROM within the connector. As a result, the programming that usually has
to be performed for the connection is not required.
All sensors and output modules can be connected to all ALMEMO®measuring
devices in the same way. The operation and programming is identical with all
units. Therefore, all of the ALMEMO®measuring system items listed below are
described, in detail, in a separate ALMEMO®manual that is supplied with every
device:
Detailed description of the ALMEMO®system (manual section 1)
Overview of the device functions and measuring ranges (manual section 2)
All sensors with basic principles, operation, technical data (man. section 3)
The options for connecting existing sensors (manual section 4)
All analogue and digital output modules (manual section 5.1)
The interface module RS232, fiber optics, Centronics (manual section 5.2)
The entire ALMEMO®networking system (manual section 5.3)
All functions and their control via the interface (manual section 6)
A complete interface command list with all print outputs (manual section 7)
These operating instructions only cover features and controls that are specific
for a certain device. As a result, the sections dealing with the system control
via keyboard will only often provide a note referring to a more detailed
description within the manual (manual section x.x.x).
4 ALMEMO2190-2
Introduction

1.1 Function Range
The multimeter ALMEMO®2190-2 is a simple measuring instrument with one
measuring input (4 channels at maximum) without an integrated programming
capability. However, it is easily possible to connect any programmed
ALMEMO®sensor and read the measured values, including the dimension,
from the LCD display. Five keys allow for reading maximum and minimum
values and for freezing or setting the measured value to zero.
An analogue output module can be connected to the output socket as required
and the measured values can, for example, be evaluated using a recorder.
SENSOR PROGRAMMING
The measuring channels are automatically programmed by the ALMEMO®
sensor connectors. It is not possible to alter the programming using the
instrument ALMEMO®2190-2, however, the programming can be changed by
means of any other ALMEMO®device that is equipped with an interface for
entering data. In any case a programming will be supported without
restrictions.
Measuring Ranges
There are corresponding measuring ranges for sensors with a non-linear
characteristic such as 10 thermocouple types, Ntc and Pt100 sensors, infrared
sensors, and flow sensors (rotating vanes, thermoanemometers, pitot tubes).
Humidity sensors are available with function channels that also calculate
humidity data such as dew point, mixture ratio, vapour pressure and enthalpy.
Even complex chemical sensors can be used. The acquisition of measured
data from other sensors is easily possible by using voltage, current and
resistance ranges with individual scaling in the connector. Existing sensors can
be used without problems. Only the corresponding ALMEMO®connector has to
be connected using its terminals. Furthermore, there are adapter connectors
with an own microcontroller for digital signals and for measuring frequencies
and pulses. This way, nearly all sensors can be connected to any ALMEMO®
measuring instrument and are interchangeable without requiring any settings.
Dimension
With any ALMEMO®sensor, two 16-segment elements will always display the
correct physical dimension. The conversion from °C to °F is automatically
performed according to the dimension.
MEASUREMENT
A maximum of 4 measuring channels is available for each sensor, i.e. it is also
possible to evaluate double sensors, sensors with different scaling or sensors
with function channels. The selected measuring point can be scanned with a
conversion rate of 2.5 measurements/second. The measured value is
calculated and indicated on the display or, if available, provided on the
analogue output.
ALMEMO2190-2 5
Functions

Measured Value
A continuous presentation of measuring data from the selected measuring
point is provided and also includes automatic zero point correction and, if
required, a correction of the measured value. A sensor breakage condition is,
with most sensors, automatically detected (exception: connectors with shunts,
dividers or additional electronics).
Measuring Functions
Some sensors require special meas. functions to achieve an optimal
acquisition of meas. data. The cold junction compensation is available for
thermocouples and a temperature compensation for dynamic pressure and pH
and conductivity probes. With infrared sensors the parameters zero point and
slope correction are used for background temperature and emissivity factor.
Maximum and Minimum Value
Each measurement involves an acquisition and storing of the maximum and
minimum value. These values can be displayed, printed or cleared.
Storage for Measured Values
The measured value can be frozen in the display by the push of a button.
Differential Measurement
By setting the measured value to zero it is possible to perform differential
measurements related to a reference value or to correct sensor errors.
External Sensor Programming
All sensor programming is supported when they have been programmed in the
factory or by using other ALMEMO®devices.
Dimension
The 2-digit dimension can be altered for each measuring channel so that the
display will always indicate the correct dimension, for example when a
transmitter is connected.
Correction of Measured Values
For correcting meas. values a zero point and slope (gain) correction can be
applied to the meas. value of a meas. channel. As a result, sensors can be
interchanged that usually, at first, require an adjustment (expansion, force, pH).
Scaling
The base value and the factor allow for a further scaling of the corrected
measured value of each measuring channel for zero point and slope (gain).
The decimal point position can be set by the exponent.
Analogue Output and Scaling
By means of analogue start and analogue end the indicated meas. value can
be scaled so that the resulting meas. range covers the full analogue output
range (2V, 10V or 20mA).
6 ALMEMO2190-2
Functions

1.2 Operating Controls
(1) ON/OFF Switch
Up: ON
Down: OFF
(2) Meas. Input M1
M1 for all ALMEMO sensors
M2 to M4 add. channels
(3) Output Socket OUTPUT
Analogue output (ZA 1601-RK)
(4) DC Socket
Mains adapter (ZB 2290-NA, 12V, 200mA)
Connect. cable (ZB 5090-EK, 7-13V DC)
Cable, electr. isol. (ZB 2290-UK, 10-30V)
(5) LCD Display
(6) Function Keys
MEASURING meas. val., meas. point
MAX fetch maximum value
MIN fetch minimum value
HOLD freeze meas. value
CLEAR set meas. value to zero
clear max, min, hold
(7) Battery Box (back of unit)
Alkaline mangan. battery 9V (6F22)
Space for spare battery
(5) LCD Display
(a) Symbols for operating modes
U battery < 7 V
BAT
 CORR correction of meas. val.
flashes differential measurement
 MAX max value
 MIN min value
 HOLD meas. value freezing
(b) 6 x 7-segment display for:
meas. point, meas. value
(c) 2 x 16-segment display for:
dimension of the meas. value
ALMEMO2190-2 7
(1) (2) (3)
(4)
(5)
(6)
(7)
2 3
BAT
Operating Controls
CORR MAX HOLD
a
bc
MIN

2. INITIAL OPERATION
1. Connect the transducers to socket M1 (2), see 4.
2. Ensure power supply with 9V battery or mains adapter, see 3.1, 3.2.
3. For switching on move the slide switch (1) on the left side of the unit to the
upper position, see 3.3.
4. For displaying the measured values:
use key MEAS. to select the measuring channels, read the meas. val., s. 7.1.
5. Use the key HOLD to perform a freezing of the measured value, see 7.3.
6. Differential measurement related to a reference value
or sensor adjustment with key CLEAR, see 7.4.
7. For evaluating the measurement:
use the keys MAX and MIN to recall the max and min values.
8 ALMEMO2190-2
Initial Operation

3. POWER SUPPLY
The following options are available for the power supply of the instrument:
9V battery IEC 6 F22 ZB 2000-B9
9V rechargeable battery,
as above with charger unit integrated in plug ZB 2000-A9, ZB 2000-LS
Mains adapter 12V/200mA ZB 2290-NA
External power supply, connecting cable ZB 2290-UK
Our product line includes corresponding accessories.
3.1 Operation with Battery and Rechargeable Battery
Only use type IEC 6 F22 alkaline manganese batteries. At a current
consumption of approximately 6mA, they last for an operating time of 60 hours.
The operating time will be shortened if sensors or modules are connected that
consume additional current.
Inserting Batteries:
The battery box (7) is located at the underside
of the instrument.
1. Press the area that is marked with the arrow and,
at the same time, pull as marked by the arrow, as
illustrated left.
2. Use the connector clip to connect the battery. The
connector shape prevents from confusing the
poles.
3. Use the second battery box to store a spare
battery.
Battery Control:
If the battery warning symbol is illuminated in the
display the battery will still operate for approx. 5 hours.
(supply voltage <7V)
If the battery voltage drops below 6 volts ´ LobAt ´ will
be indicated on the display.
The battery should be immediately removed. Leakage
of the battery and damage to the instrument can then
be avoided.
The actual battery voltage can be accurately monitored with an
own measuring channel Ubat and the remaining battery life can
be estimated accordingly.
ALMEMO2190-2 9
Power Supply

Tips regarding correct handling of batteries:
Do not leave used batteries in the instrument!
Remove batteries from the instrument if it is not used for a long period.
Risk to health and instrument failure can result from leaking batteries!
Therefore, only use leak-proof batteries.
Used batteries are hazardous waste and must be disposed in an
environmentally friendly way! Return them to the dealer or dispose of
them in a battery storage container.
Operation with Rechargeable Batteries
Rechargeable batteries can be used instead of normal batteries. Due to their
smaller capacity of 110mAh they only reach an operating time of 20 hours. The
operating time will be shortened if sensors or modules are connected that
consume additional current. It is recommended to use the 9V rechargeable
battery with plug-integrated charger unit ZB 2000 LS, which is included in the
range of accessories.
Tips regarding correct handling of rechargeable batteries:
The rechargeable batteries supplied are not charged when delivered!
If NiCd cells are only partly discharged, the full capacity cannot be
reached by a normal recharging.
Therefore, use the instrument until the rechargeable batteries are
completely discharged.
Completely recharge the rechargeable batteries afterwards.
As a result, the life of the rechargeable batteries is significantly
increased.
Completely recharged batteries will slowly discharge during storage.
3.2 External Voltage Supply
For an external voltage supply the connector socket (4) is located at the right
side of the device. The range of accessories includes the mains adapter ZB
2290-NA (12V/200mA). However, any other DC voltage source (7 to 13V) can
also be used. The connection is performed by a low-voltage connector (NES1
according to DIN 42323, centre pin to negative).
The electrically isolated supply cable ZB 2290-UK must be used if an
electrical isolation between power supply and transducers is required or if a
larger input voltage range (10...36V DC) is required. It allows to operate the
measuring instrument with 12V or 24V mains supply.
If a battery is used in addition it will take over the power supply
if the voltage drops under 9V.
10 ALMEMO2190-2
Power Supply

3.3 Switch On/Off
The ON/OFF switch (1) on the left side of the device has two positions:
up: ON
down: OFF
For switch-on the slide switch (1) on the left side must be moved upwards.
The device is switched off when the slide switch is moved to the lower
position.
Measuring data will be lost; however, the sensor programming in the
ALMEMO®connectors will not be affected.
4. CONNECTION OF THE TRANSDUCERS
Any ALMEMO®sensors can be connected to the ALMEMO®input socket M1
(2). For connecting existing sensors it is only necessary to connect a
corresponding ALMEMO®connector.
4.1 Transducers
A detailed description of the comprehensive ALMEMO®sensor range (see
manual section 3) and the connection of existing sensors (see manual section
4) to the ALMEMO®instruments are provided in the ALMEMO®manual. All
standard sensors with ALMEMO®connector usually have the measuring range
and dimension already programmed and can be immediately connected to any
input socket. A mechanical coding ensures that sensor and output modules
can only be connected to the correct sockets. Furthermore, each ALMEMO®
connector has two locking levers that snap in when the insertion into the socket
is established and that prevent a disconnection caused by pulling the cable.
Both levers must be pressed on the sides for disconnecting the connector.
4.2 Measuring Inputs and Additional Channels
The measuring instrument ALMEMO®2190-2 has 1 input socket M1 (2), the
ALMEMO®2290-3 has 2 input sockets M1 and M2, and additionally a
differential channel M3 (M1-M2). However, ALMEMO®sensors can, if required,
provide up to 4 channels. The additional channels can be especially used with
humidity sensors with 4 measuring variables (temperature/humidity/dew
point/mixture ratio) or used for function channels. If required, a sensor can also
be programmed with several ranges or scaling or, depending on the pin
assignment, 2 or 3 sensors can be combined in one connector (e.g. rH/Ntc,
mV/V, mA/V etc.). The additional measuring channels of the connector are
located next to the first channel. The following channel occupancy is valid for
both measuring instruments.
ALMEMO2190-2 11
Connection of the Transducers

Combined sensors within one connector are electrically
connected to each other and must, therefore, be operated in
isolation. The voltage applied to the measuring inputs must not
exceed ±5V (between B,C,D and A or - respectively).
The cold junction compensation for thermocouple measurement is integrated
in socket M1 of the device.
1
2
3
4
chann. 1
chann. 2
chann. 3
chann. 4
M1 OUTPUT
2190-2
12 ALMEMO2190-2
Connection of the Transducers

5. DISPLAY
The display (5) of the measuring instrument ALMEMO®2190-2 consists of an
LCD module with six 7-segment digits, two 16-segment digits, and a battery
symbol and seven arrows for indicating the operating status.
CORR MAX MIN HOLD (CONT)
M DIM
Special Operating Conditions
Segment test of the display automatically after switch-on.
Supply voltage: lower than 7 V: symbol illuminated
BAT
lower than 6 V: 1:L o b A t
Sensors that are not connected,
deactivated measuring points,
cleared programming values.
Sensor correction or scaling: arrow CORR illuminated
Measurement in differential mode: arrow CORR flashes
Display max value: arrow MAX illuminated
Display min value: arrow MIN illuminated
Measured value frozen: arrow HOLD illuminated
Continuous measuring point scan: arrow (CONT) illuminated
Alarm Conditions
Sensor breakage: abbr. flashes
1: N i C r °C
Overshooting of measuring range: maximum value flashes
Undershooting of measuring range: minimum values flashes
Undershoot of meas. range CJ compens. (cold junction)
or CJC breakage: flashes
Exceeding of range of values (>65000): flashes
1:6 5 0 0 0
2 3
BAT
1: - - - -XX
1: C J
ALMEMO2190-2 13
Display

6. SENSOR PROGRAMMING
As all ALMEMO®instruments contain the whole sensor programming stored in
the ALMEMO®connector, it is possible to connect all ALMEMO®sensors with
no programming being required. The instrument ALMEMO®2190-2 does not
offer any programming facility. To connect existing sensors it is necessary to
order an ALMEMO®connector including the corresponding programming.
However, if sensors must be scaled or if sensor errors must be reliably
corrected, it is also possible to perform the programming (s. man. 6.3) using
other ALMEMO®instruments that provide input capabilities.
6.1 Measuring Ranges
With each channel switching or in case of a sensor breakage the abbreviation
of the measuring range is indicated in the display. For easy identification the
following table provides all possible measuring ranges.
Transducer Sensor/Cable Meas. Range Dim Display
Pt100-1 FP Axxx -200.0... +850.0 °C P104
Pt100-2 FP Axxx -200.00...+200.00 °C P204
Ni100 ZA 9030-FS3 -60.0... +240.0 °C N104
NiCr-Ni (K) FT Axxx -200.0...+1370.0 °C NiCr
NiCroSil-NiSil (N) ZA 9020-FSN -200.0...+1300.0 °C NiSi
Fe-CuNi (L) ZA 9000-FSL -200.0... +900.0 °C FECO
Fe-CuNi (J) ZA 9000-FSJ -200.0...+1000.0 °C IrCo
Cu-CuNi (U) ZA 9000-FSU -200.0... +600.0 °C CUCO
Cu-CuNi (T) ZA 9000-FST -200.0... +400.0 °C CoCo
PtRh10-Pt (S) FS Axxx 0.0...+1760.0 °C Pt10
PtRh13-Pt (R) ZA 9000-FSR 0.0...+1760.0 °C Pt13
PtRh30-PtRh6 (B) ZA 9000-FSB +400.0...+1800.0 °C EL18
Au-FeCr ZA 9000-FSA -270.0... +60.0 °C AUFE
Ntc type N FN Axxx -30.00...+125.00 °C Ntc
Millivolt ZA 9000-FS0 -10.000...+55.000 mV U 55
Millivolt 1 ZA 9000-FS1 -26.000...+26.000 mV U 26
Millivolt 2 ZA 9000-FS2 -260.00...+260.00 mV U260
Volt ZA 9000-FS3 -2.6000...+2.6000 V U2.60
Differential Millivolt ZA 9050-FS0 -10.000...+55.000 mV d 55
Differential Millivolt 1 ZA 9050-FS1 -26.000...+26.000 mV d 26
Differential Millivolt 2 ZA 9050-FS2 -260.00...+260.00 mV d260
Differential Volt ZA 9050-FS3 -2.6000...+2.6000 V d2.60
Sensor Voltage any 0.00...20.00 V UbAt
Milliampere ZA 9601-FS1 -32.000...+32.000 mA I032
Percent (4-20mA) ZA 9601-FS2 0.00... 100.00 % P420
Ohm ZA 9003-FS 0.00... 400.00 ΩOhn
Frequency ZA 9909-AK1 0... 25000 Hz FrEq
Pulses ZA 9909-AK2 0... 65000 PULS
14 ALMEMO2190-2
Sensor Programming

Transducer Sensor/Cable Meas. Range Dim Display
Digital Input ZA 9000-EK2 0.0... 100.0 % Inp
Digital Interface ZA 9919-AKxx -65000... +65000 diGi
Infrared 1 FI A628-1/5 0.0... +200.0 °C Ir 1
Infrared 2 FI A628-2 0.0... +800.0 °C Ir 2
Infrared 3 FI A628-3 -30.0... +70.0 °C Ir 3
Infrared 4 FI A628-4 -30.0... +100.0 °C Ir 4
Infrared 6 FI A628-6 0.0... +500.0 °C Ir 6
Snap-on head Normal 20 FV A915-S120 0.30... 20.00 m/s S120
Snap-on head Normal 40 FV A915-S140 0.40... 40.00 m/s S140
Snap-on head Micro 20 FV A915-S220 0.50... 20.00 m/s S220
Snap-on head Micro 40 FV A915-S240 0.60... 40.00 m/s S240
Macro FV A915-MA1 0.10... 20.00 m/s L420
Water-Micro FV A915-WM1 0.00... 5.00 m/s L605
Dyn.press. 40m/s w. TC a. PC FD A612-M1 0.50... 40.00 m/s L840
Dyn.press. 90 m/s w. TC a. PC FD A612-M6 1.00... 90.00 m/s L890
Rel. air humidity cap. FH A646 0.0... 100.0 %H °orH
Rel. air humidity cap. w. TC FH A646-R 0.0... 100.0 %H H rH
Mixture rario w. PC FH A646 0.0 ... 500.0 g/k H AH
Dew point temperature FH A646 -25.0... 100.0 °C H dt
Partial vapour pressure FH A646 0.0 ...1050.0 mb H UP
Enthalpy w. PC FH A646 0.0 ... 400.0 kJ H En
Humid temperature FN A846 -30.00 ... +125.00 °C P Ht
Rel. humidity psychr. w. PC FN A846 0.0 ... 100.0 %H P RH
Mixture ratio w. PC FN A846 0.0 ... 500.0 g/k P AH
Dew point temperature w. PC FN A846 -25.0 ... +100.0 °C P dt
Partial vapour press. w. PC FN A846 0.0 ...1050.0 mb P UP
Enthalpy w. PC FN A846 0.0 ... 400.0 kJ P En
Conductivity probe w. TC FY A641-LF 0.0 ... 20.000 mS LF
CO2sensor FY A600-CO2 0.0 ... 2.500 % CO2
O2saturation w. TC a. PC FY A640-O2 0 ... 260 % O2-S
O2concentration w. TC FY A640-O2 0 ... 40.0 mg O2-C
Function channels:
Difference any diFF
Maximum value any Hi
Minimum value any Lo
Average value over time any A[t]
Average value over junctions any A[n]
Sum over junctions any S[n]
Total number of pulses ZA 9909-AK2 0... 65000 S[t]
Pulses/print cycle ZA 9909-AK2 0... 65000 S[P]
Alarm value any % Alrm
TC=Temperature Compensation, PC=Atmospheric Pressure Compensation
ALMEMO2190-2 15
Sensor Programming

6.2 Dimension
The dimension is indicated by two 16-segment digits next to the measured
value. Depending on the programming (see also manual 6.3.5) the dimension
can be different from the standard dimensions of the measuring range (see
6.1).
When the dimension °F is selected a temperature value in
degrees Celsius will be converted into degrees Fahrenheit.
The cold junction compensation can be switched off by using the
character Cor F. The dimension ms is indicated in the display
as m/s, and mh as m3/h.
7. MEASUREMENT
The instrument ALMEMO®2190-2 provides the following options for the
acquisition of measuring data:
1. Continuous measurement of a selectable measuring point, see man. 6.4
Output of measuring data to the analogue output, see manual 5.1.1.
2. Single measuring point scan, see manual 6.5.1.3.
The following functions are available for the data processing:
1. Storage of maximum and minimum value.
2. Freezing of the measured value.
3. Differential measurement based on a reference value.
7.1 Measured Value and Selection of a Meas. Point
If no continuous measuring point scan has been programmed, only the
measured value of the selected measuring point will be continuously acquired.
This is the standard operating mode and is most suitable for recording with an
analogue output.
After switching on, the display will immediately indicate the actual measured
value of measuring point 1 (M1).
Function MEASUREMENT
HOLD
MIN
MAXCORR
MDIM
If more than one measuring point has been programmed in the connected
sensor (e.g. humidity sensor), the remaining (2 to 4 at max.) measuring points
can be selected using the key MEAS.. If the key MEAS. is pressed longer
(approx. 1s) the previous channel will be indicated again.
16 ALMEMO2190-2
Measurement

Selection of further meas. points with key:
MESSEN HOLD
MIN
MAXCORR
M
DIM
If the measuring range changes when switching over, the abbreviation of the
measuring range is indicated for a short time (s. 6.1). In case of a sensor
breakage the abbreviation flashes instead of the measured value:
Display measuring range:
HOLD
MIN
MAXCORR
MDIM
If the actual measured value has been changed by scaling or correction values
(see man. 6.3.10/11) the arrow ´CORR´ will be indicated on the display.
If the difference to a reference value is indicated for a short time, the arrow
´CORR´ will flash (see 7.4).
7.2 Maximum and Minimum Values
The maximum and the minimum value are always determined among the
current measured values of a measuring point and are stored. For displaying
the peak values the required channel must be selected (see 7.1) and the key
MAX or MIN must be pressed. For control purposes an arrow will be indicated
under the corresponding symbols.
Function MAX VALUE
Selection of max value with key:
MAX
HOLD
MIN
MAXCORR
MDIM
Function MIN VALUE
Selection of min value with key:
MIN
HOLD
MIN
MAXCORR
MDIM
Clear max/min values with key:
LÖSCHEN
Return to the meas. value with key:
MESSEN
ALMEMO2190-2 17
Measurement

7.3 Memory for Momentary Values
If a measured value, e.g. for easier evaluation, is frozen at a certain point in
time, the key HOLD must be operated. The hold mode is indicated in the display
by an arrow under the ´HOLD´ symbol.
Function HOLD
Freezing of measured value with key:
HOLD HOLD
MIN
MAXCORR
M
DIM
With each additional operation of the key HOLD, the momentary measured
value will be taken over and displayed.
To return to a continuous display of the current measured value, the key CLEAR
or MEAS. must be pressed. The arrow ´HOLD´ will turn off.
7.4 Differential Meas. and Correction of Meas. Values
In the function MEASUREMENT the key CLEAR can be used to set the current
measured value to zero, i.e. the current measured value will be stored as
reference value and the difference to this reference value will be displayed. To
indicate the differential mode the arrow ´CORR´ will flash in the display.
Set measured value to zero with key:
LÖSCHEN
HOLD
MIN
MAXCORR
M
DIM
When a zero setting is performed, the max and min values of this channel will
be automatically cleared.
If a base value has been programmed (see man. 6.3.11) the
measured value will not be zero but the negative base value after
the adjustment.
For example, if the temperature is set to zero at a certain point, the differences
to the reference point can be read at any point. The MAX, MIN and HOLD
functions are also available when difference measurements are performed.
The reference value will only be cleared when the key MEAS. is operated again
in the function MEASUREMENT or when the instrument is being switched off.
In this case the max and min values will also be cleared and the arrow ´CORR´
will stop flashing.
18 ALMEMO2190-2
Measurement

Sensor Adjustment
The function differential measurement is also suitable for the correction of
measured values of a sensor. Many sensors must be adjusted more frequently
to compensate for instabilities.
In most cases, a temporary zero point correction will be sufficient.
Firstly, the measured value must be brought to zero, i.e.:
Temperature sensors must be put into ice water
Pressure and force transducers must be released
Hoses of dynamic pressure probes must be removed or
Pitot tube must be removed from the flow channel
pH probe must be placed in pH 7 buffer solution
Conductivity probe must be taken out of the substance and dried
Afterwards, the display of the measured value can be set to zero by operating
the key CLEAR. This procedure corresponds to a zero point adjustment, as
described in the manual section 6.3.10. For probes with a scaling the base
value will be maintained, i.e. a pH probe will not indicate pH 0.00 but pH 7.00
after the adjustment.
Unlike other ALMEMO®instruments, the correction values will not
be stored in an EEPROM of the sensor but will be lost when
switching over in function MEASUREMENT or when switching the
instrument off.
With the following sensors a slope correction can be performed in addition,
when a corresponding calibration value is provided at the sensor:
pH probe FY A8PH-xx: pH 4.0 or pH 10.0
Conductivity FY A641-LF: 2.77 mS/cm
or FY A641-LF2: 147 µS/cm
O2saturation FY A640-O2: 101 %
7.5 Continuous Measuring Point Scan
To also obtain the max and min values of those measuring points that are not
indicated and to ensure a continuous temperature compensation of probes for
pH and dynamic pressure, it is possible to set a continuous measuring point
scan for sensors with several channels (see man. 6.5.1.3).
The continuous measuring point scan can be activated by pressing the key
MEASUREMENT during switching on the instrument. For control purposes an
arrow will be indicated in the display on the right above the dimension. When
switching off, the instrument will return to the standard setting.
Press key when switching on the instrument:
MESSEN
HOLD
MIN
MAXCORR
M
DIM
ALMEMO2190-2 19
Measurement

8. TROUBLESHOOTING
The measuring instrument ALMEMO®2190-2 allows for a connection of many
different sensors and peripheral devices. Due to the large variety of options it is
possible that, under certain conditions, it does not perform as the user would
expect. In most cases this will not be related to a defective device but to
operating errors such as wrong settings or an inadmissible wiring. The
following tests should be performed to correct or to correctly identify the error.
Error: No display data or all display segments are permanently illuminated.
Remedy:Check power supply, switch off and on again.
Error: False measured values.
Remedy:Press key MEAS.VALUE to clear a reference value that might exist.
Error: Varying meas. values, segment test or blockage during operation.
Remedy:Check cabling for inadmissible electrical connection.
Disconnect external power supply and output modules.
Disconnect all suspicious sensors and replace them by hand-held
sensors operated in air or by dummies (short circuit AB at
thermocouples, 100Ωat Pt100 sensors).
If this corrects the error, check the wiring, isolate the sensor if
necessary, and prevent influences from disturbances by shielding or
twisting.
If the device is, after the above inspections, still not performing as specified in
the operating instructions, it must be sent to the factory in Holzkirchen,
Germany, including a short report and possibly control printouts.
20 ALMEMO2190-2
Troubleshooting