MMF M208A User manual

Instruction Manual
Manfred Weber
Metra Mess- und Frequenztechnik in Radebeul e.K.
Meissner Str. 58 - D- 1445 Radebeul
Phone [phone] Fax [phone]
Email: [email protected] Internet: www.MMF.de
8 Channel
IEPE
Conditioner
M208A
From Version 1. 12

Manfred Weber
Metra Mess- und Frequenztechnik in Radebeul e.K.
Meissner Str. 58
D-01 5 Radebeul
Phone + 9-351-836 2191
Fax + 9-351-836 29 0
Email [email protected]e
Internet www.MMF.de
Notice: The current version of this document can be downloaded from
http://www.mmf.de/product_literature.htm
Specifications subject to change without prior notice.
© 2009 Manfred Weber Metra Mess- und Frequenztechnik in Radebeul e.K.
No part of this document may be reproduced without the prior written consent of Metra.
Nov/ 22

Contents
1. Application............................................................................................................5
2. The Instrument at a Glance....................................................................................5
2.1. Connectors and Controls................................................................................5
2.2. Display Functions...........................................................................................6
2.3. Menu Structure...............................................................................................6
3. What is IEPE?........................................................................................................7
. What is TEDS?......................................................................................................8
5. Description..........................................................................................................11
6. Power Supply......................................................................................................12
7. Inputs and IEPE Supply.......................................................................................12
8. Outputs................................................................................................................13
9. Grounding and Avoiding Ground Loops ............................................................1
10. Operation ..........................................................................................................1
10.1. Gain Selection............................................................................................1
10.2. Transducer Sensitivity................................................................................1
10.2.1. Introduction........................................................................................1
10.2.2. Normalization of the Display..............................................................16
10.2.3. Normalization of the Amplifier Output...............................................16
10.2. . Sensor Detection.................................................................................17
10.2.5. Entering Transducer Sensitivity in the Menu......................................18
10.2.6. Automatic Sensitivity Adjustment with TEDS Sensors......................18
10.3. Channel Registration..................................................................................19
10. . Measuring Unit...........................................................................................20
10.5. Display Mode.............................................................................................20
10.6. Measuring Display.....................................................................................21
10.7. Relative Magnitude and Overload Indication.............................................21
10.8. Relay Output..............................................................................................22
11. Filters and Integrators........................................................................................2
11.1. Filters ........................................................................................................2
11.2. Integrators..................................................................................................26
11.3. Replacing Filter and Integrator Modules ...................................................28
11. . Detection and Display of Filters and Integrators........................................29
11.5. Switching Off the High Pass Filters...........................................................30
12. Other Settings....................................................................................................31
12.1. Beep...........................................................................................................31
12.2. Serial Interface...........................................................................................31

12.3. Ethernet Interface.......................................................................................31
12. . Switching the IEPE Supply On or Off........................................................31
12.5. Instrument Name........................................................................................32
12.6. Loading Default Settings............................................................................32
12.7. Overload Limits..........................................................................................33
12.8. Firmware Update........................................................................................3
13. PC Connection...................................................................................................35
13.1. Serial Interface...........................................................................................35
13.1.1. Settings...............................................................................................35
13.1.2. Linking Several M208A Units............................................................35
13.1.3. PC Software M208 Control Center.....................................................36
13.1.3.1. Introduction.................................................................................36
13.1.3.2. System Requirements...................................................................36
13.1.3.3. Controls and Functions................................................................37
13.1.3.3.1 Device Menu.........................................................................38
13.1.3.3.2 Device Channels.................................................................... 0
13.1.3.3.3 Channel Overview ................................................................ 3
13.1.3.3. Other menus..........................................................................
13.1.3.3.5 Function Keys....................................................................... 6
13.1.3.3.6 Error Messages...................................................................... 6
13.1. . Communication via ASCII Commands............................................... 7
13.1. .1. Introduction................................................................................. 7
13.1. .2. Control Commands...................................................................... 8
13.1. .3. Read commands...........................................................................50
13.2. Ethernet Interface.......................................................................................52
13.2.1. Introduction........................................................................................52
13.2.2. TCP/IP Settings...................................................................................52
13.2.3. Establishing an Ethernet Connection..................................................53
1 . Reset..................................................................................................................5
15. Calibration.........................................................................................................55
15.1. General.......................................................................................................55
15.1.1. Gain Calibration..................................................................................55
15.2. Display Calibration.....................................................................................55
16. Version and Serial Number................................................................................56
17. Frequently Asked Questions..............................................................................56
18. Technical Data...................................................................................................58
Appendix: Warranty
CE Declaration of Conformity

Thank you for using a vibration instrument from Metra!
1. Application
The 8 Channel IEPE Conditioner M208A was designed for piezoelectric accelerom-
eters, force transducers, pressure transducers and measuring microphones with IEPE
output. The instrument has the following functions:
•Constant current supply of up to eight sensors
•Gain ranges of 0, 20, 0 and 60 dB
•Normalization of transducer sensitivity
•High pass and low pass filtering, optionally single and double integration
In addition, the M208A can display RMS or peak values including physical units.
A relay output is available for controlling external devices. The M208A features a
serial interface for setup and readout by a supplied PC software. The Ethernet inter-
face and the embedded web server of the instrument provide network and Internet
connectivity.
2. The Instrument at a Glance
2.1. Connectors and Controls
5
Figure 1: Front and rear panels
2
4
6
dB
IEPE
OVL
IN O U T
8
SW IT C H E D
O U T P U T
M 2 0 8
8 C H A N N E L IE P E
Display
LEDs for gain indication
Overload LED
Constant current LED
Output socket (channel 8)
Input socket (channel 8)
Shared output (channels 1 to 8)
Arrow keys for menu navigation
Escape key for leaving menus
Key for sensor setup
Key for gain menu
OK key for confirming selections
Key for setup menu
Front Panel:
ear Panel:
+ 1 ...2 6 V D C
3 A
G N D
RESET
P C / M A S TE R
S L AV E
O U T P U T 1 ... 8
R S - 23 2
E T H E R N E T
SE R IAL N O .: M A D E IN G E R M A N Y
Ethernet socket
Serial interface to PC or master unit
Serial interface to slave unit
Outputs of channels 1 to 8 and relay output
Link LED
Active LED
Ground socket
Power supply socket
Reset key
POWER
On/Off switch

2.2. Display Functions
2.3. Menu Structure
6
MENU
1/6: Filter setup
2/6: Display unit
3/6: Display mode
4/6: Channel on/off
5/6: Alarm relay
6/6: Div. settings
1/2: Filter detection
2/2: Highpass on/off
1/9: Beeper
2/9: Serial Interf.
3/9: Ethernet
6/9: Instrument name
5/9: Factory setup
7/9: Load defaults
8/9: Overload limits
4/9: IEPE on/off
(password protected)
9/9: Firmware update
Figure 2: Display in measuring mode
Transducer sensitivity
Displayed
channel
Measuring value
Physical unit
Display mode RMS
Rel. magnitude
Press OK to stop
channel rotation
Press OK for channel rotation
High pass and low pass filter
Relay output
Display mode Peak
Rel. magnitude
below 5 % of full scale

3. What is IEPE?
The M208A is a signal conditioner for sensors with IEPE output. The abbreviation
stands for Integrated Electronics Piezo Electric and is a common industrial standard
for the output of piezoelectric sensors and microphones. Proprietary brand names,
like ICP®, Isotron®, Deltatron®, Piezotron® etc., are also used for the same purpose.
An electronic circuit inside the sensor transforms the high-impedance signal of the
sensing element into an output signal with low impedance, which can more easily
be transmitted and processed.
A distinctive feature of IEPE is the transmission of supply current and measuring
signal via one single wire, so an IEPE transducer is connected via a coaxial cable.
3 shows the principle circuit of an IEPE measuring chain. To supply the sensor elec-
tronics, constant current is used (not to be confused with -20 mA current loops).
The constant current is fed into the signal cable by the signal conditioner. A cou -
pling capacitor keeps the DC components away from the AC signal path.
When constant current is fed into the sensor, a positive DC voltage, called bias volt-
age, arises at the sensor terminals. Depending on model and manufacturer, the bias
voltage can be in the range from 5 to 1 V. The bias voltage is modulated with the
measuring signal usensor. The sensor output can never become negative. The mini-
mum output voltage is approximately 1 V, the saturation voltage of the sensor out-
put stage. The upper voltage limit is determined by the supply voltage of the con-
stant current source, also called compliance voltage. The M208A uses 2 V.
shows the dynamic range of an IEPE transducer.
7
Figure 3: IEPE principle
Integated electronics
U = 24VDC
I
= 4mA
const
s
QU
Sensing element
I
const
Constant supply current
U
s
Supply voltage of constant current source
Coaxial cable
> 1 m
IEPE Sensor M208
U
bias
+u
sensor
LED
sensor
indication
Filter
Amplifier Buffer
eadout unit
- 6 dB

The M208A features a circuit for sensor check. It can detect the following condi-
tions, based on the sensor output voltage:
•No sensor present (yellow LED off, no measuring value for this channel)
•Sensor detected (yellow LED on, measuring value displayed)
•Short circuit at input (display “IEPE SHORT”)
The constant current supply can be switched off for each channel (see section 12. .
on page 31). The sensor detection will then also be deactivated.
4. What is TEDS?
The M208A includes full TEDS support.
The abbreviation TEDS stands for “Transducer Electronic Data Sheet”. It specifies
sensors containing a memory device holding their most important characteristics.
An advantage of TEDS is that these characteristics are associated with the sensor
and cannot get lost. The measuring system can configure itself without entering any
data manually after the sensor being plugged in.
IEEE 1 51 describes the memory, the interface and the arrangement of data. In part
of this standard a sub-group of TEDS transducers is described which is compati-
ble with IEPE inputs. The memory can be accessed via the signal cable by means of
a negative logical pulse chain. When these sensors are supplied by constant current,
they perform like normal IEPE sensors. 5 shows the principle of TEDS.
8
Figure : Dynamic range of IEPE sensors
Max. sensor output =
supply voltage of constant current source
(24 V with M2 8)
Sensor saturation voltage
(approx. 1 V)
Sensor bias voltage
(see data sheet)
negative overload
V
positive overload
Sensor dynamic range

TEDS sensors include a memory device DS2 30A with a so-called 1-Wire® inter-
face made by Dallas/Maxim. This memory is divided into a 6 bit ROM portion,
called application register, which may be programmed once, and a re-programmable
256 bit EEPROM portion.
The application register, called the basic TEDS, contains data stored by the manu-
facturer. This data cannot be edited. It includes:
•Manufacturer code
•Type identifier
•Version number
•Version letter
•Serial number
The EEPROM holds sensor data which may be edited for calibration purposes.
Type and arrangement of this data depends on the TEDS template used. Standard
templates are published on the IEEE server at http://standards.ieee.org/regauth/1 51
In addition there are proprietary manufacturer templates.
The M208A supports the standard template no. 25 for piezoelectric accelerometers
and force transducers and the template nos. 27 and 28 for measuring microphones.
These templates allow the specification with or without a transfer function by means
of switch bits.
9
Figure 5: TEDS principle
U
I
const
s
C
k
Coaxial cable
IEPE Sensor with TEDS to IEEE 1451.4
Signal
conditioning
TEDS
Memory
Ampl.
TEDS
read / write
interface
- Manufacturer
- Model
- Version
- Serial number
- Sensitivity
- Direction, polarity
- Weight
- Frequency range
- Amplitude linearity
- Temperature coefficient
Sensing
element
IEPE
supply
- User text
- Measuring ID
Written only
by the
manufacturer
Written by the
manufacturer
and calibration
labs
Written by the
user

Template No. 25 for piezoelectric accelerometers and force transducers:
Without transfer function: With transfer function:
•Sensitivity
•Lower frequency limit
•Measuring direction
•Weight
•Polarity
•Calibration frequency
•Calibration temperature
•Calibration date
•Calibration initials
•Calibration interval
•ID of measuring point
•User text
•Sensitivity
•Lower frequency limit
•Measuring direction
•Weight
•Polarity
•Low pass frequency
•Resonance frequency
•Resonance quality
•Amplitude slope
•Temperature coefficient
•Calibration frequency
•Calibration temperature
•Calibration date
•Calibration initials
•Calibration interval
•ID of measuring point
•User text
Template No. 27 for measuring microphones:
Without transfer function: With transfer function:
•Sensitivity
•Reference frequency
•Reference polarization voltage
•Microphone type
•Microphone size
•Equivalent volume
•Polarity
•Calibration date
•Calibration initials
•Calibration interval
•ID of measuring point
•User text
•Sensitivity
•Reference frequency
•Reference polarization voltage
•Microphone type
•Microphone size
•Equivalent volume
•Actuator / correction
•High pass frequency
•Resonance frequency
•Resonance quality
•Polarity
•Calibration date
•Calibration initials
•Calibration interval
•ID of measuring point
•User text
10

5. Description
6 shows the block diagram of the M208A. The instrument includes eight identical
analog signal paths for amplification and filtering. A micro controller unit controls
the analog part, provides digital interfaces, key control and display functions.
The sensor signals enter the M208A via BNC sockets on the front panel. The IEPE
constant current sources may be switched off individually. The input is followed by
an amplifier stage with selectable gains of 0 or 20 dB. High pass and low pass filters
are designed as plug-in modules. The high pass can be switched off. There are also
single and double integrator modules which may be plugged in instead of the filters.
A selectable attenuator stage is followed by a digital-to-analog converter for fine
gain tuning. It is used for transducer normalization. Before the output there is an-
other selectable amplifier stage and a buffer. Splitting the gain before and after the
filters helps to avoid overload at frequencies in the filter stop band. The output is
accessible on the front panel via BNC sockets and on the rear panel via a Sub-D
connector. There is a shared output which can be switched to channels 1 to 8.
The analog-to-digital converter of the micro controller unit measures the output
voltage of each channel for one second. It can display RMS or peak values. The dis -
played measuring values can be used to trigger a relay output which is also con-
nected to the Sub-D connector on the rear panel.
Model M208A supports sensors with TEDS to IEEE 1 51. . Sensors are automati-
cally identified after connection. The stored sensitivity is read and the amplifier gain
is normalized accordingly to provide a gain in volts per mechanical unit.
An RS-232 interface and an Ethernet interface serve for external control and read-
out. Up to eight M208A units can be controlled via one RS-232 interface by con-
necting them to each other using the master and slave interfaces.
The M208A is powered from a DC voltage source.
11
Figure 6: Block diagram
I
const
Input 1
BNC
DAC
-2 .. dB
Output 1
2 dB
I
const
Input 8
BNC
DAC
-2 .. dB 2 dB
Channels 1 to 8
Shared
output
MUX
1-8
Sub-D
BNC
Output 8
Sub-D
BNC
Sub-D
BNC
Digital control
RMS/PEAK
display
Sensor
check Micro
controller
Ethernet RS-232
TEDS Relay
output
Low pass
module
High pass
module
-2 / dB
/2 dB /2 dB
-2 / dB /2 dB
/2 dB
1
8
Low pass
module
High pass
module

6. Power Supply
The M208A is powered by an external DC supply voltage from 10 to 28 V. This
could be a supplied mains adapter or a car battery, for example. Current consump-
tion is below 1.5 A. The supply voltage is connected by a circular power connector
to DIN 5323. 7 shows the polarity of this socket.
The M208A is protected against false polarization.
There is a fuse inside the instrument. For replacing the fuse, remove the four screws
holding the cover plate and open the case. The location of the fuse holder is shown
in 8. The fuse must be rated 2 A (slow).
Unplug the power supply before replacing the fuse!
Ground your hands before touching electronic components inside!
Use only fuses with the appropriate rating!
7. Inputs and IEPE Supply
The M208A has eight identical measuring channels. Sensors are connected via BNC
sockets marked “IN” on the front panel. The input impedance is approximately
MΩ. The input overload limit is ± 10 V. The inputs can withstand voltages of up
to ± 25 V.
For the operation with IEPE sensors constant current sources must be switched to
the inputs (see 12. on page 31). By default the M208A is equipped with mA con-
stant current sources which is a practical value for most applications. For extremely
long sensor cables and high frequencies to be measured, the instrument can also be
equipped with 8 mA sensor supplies. The constant current source module can be re-
placed by the user. Open the cover plate after removing four screws (see 9).
Unplug the power supply before replacing the module!
Ground your hands before touching electronic components inside!
12
Figure 7: Polarity of the
supply socket
Figure 8: Location of the fuse holder

8. Outputs
The eight outputs are accessible via BNC sockets (“OUT”) on the front panel and a
25 pin Dub-D connector on the rear panel (10).
The outputs are short-circuit-proof. Their output impedance is 100 Ω.
In addition to the channel outputs there is a shared output which can be connected to
one of the channels. It is accessible via the BNC socket “SWITCHED OUTPUT” on
the front panel and the Sub-D connector on the rear panel (10).
The shared output is always switched to the channel which is currently measured.
The M208A performs multiplex measurement with an interval of 1 s. Multiplexing
may be stopped at a desired channel by pressing the OK key. Then the selected
channel is permanently connected to the shared output. Multiplexing can be started
by pressing OK again.
The 25 pin Sub-D connector also provides some of the internal DC supply voltages
for external purposes. Please make sure not to load these outputs with more than
20 mA each.
9. Grounding and Avoiding Ground Loops
All inputs and outputs are referred to the same ground potential. Ground is also
available at the socket (“GND”) on the rear panel.
13
Figure 9: Location of the constant current source module
Figure 10: Sub-D output
socket
Shared output
Ground
1
23
45678
Outputs
+3.3V
+12V
-12V

The negative supply Terminal (-) is also connected to ground.
To prevent ground loops it is recommended that additional connections are not
made between the sensor cases via the test object. This can be avoided by using sen-
sors with isolated base or isolating pads which are available as accessory parts.
10. Operation
10.1. Gain Selection
The instrument has four gain ranges of 0, 20, 0 and 60 dB (1, 10, 100 and 1000),
which may be set for each channel individually.
Open the gain menu by pushing the “GAIN” key. Select the desired channel
(“Channel No.:”) using the ▲▼ and OK keys. Selection “all” will set the gain of
channels 1 to 8 simultaneously. After this select the desired gain range in the same
way. You may leave the menu without making changes by pressing ESC.
The selected gain ranges are indicated by a combination of LEDs on the front panel
for each channel:
0 dB: LEDs off
20 dB: orange LED (“20”)
0 dB: green LED (“ 0”)
60 dB: orange and green LED
10.2. Transducer Sensitivity
10.2.1. Introduction
The purpose of entering transducer sensitivity is to normalize output of the measur-
ing chain, consisting of the sensor and the M208A, to a physical unit. The actual
gain of the M208A will not be 0, 20, 0 or 60 dB but an odd value providing a rela-
tion between output voltage and measured physical quantity in multiples of ten.
This simplifies the interpretation of the measuring signal. Adjusting the readout
equipment to the sensor is no longer necessary.
1
Figure 11: Gain selection

Example: Accelerometer with a sensitivity of 11.2 mV/ms-2
M208A output without normalization: 0 dB → 11.2 mV/ms-2
20 dB → 112 mV/ms-2
0 dB → 1.12 V/ms-2
60 dB → 11.2 V/ms-2
M208A output with normalization: 0 dB → 10.0 mV/ms-2
20 dB → 100 mV/ms-2
0 dB → 1.00 V/ms-2
60 dB → 10.0 V/ms-2
Normalization is done by entering transducer sensitivity in millivolts per mechani-
cal unit. Permissible values are between 1 and 12. At a sensitivity of 1 the M208A
works with its basic gain ranges of 0, 20, 0 and 60 dB (1, 10, 100 and 1000) see
section 10.1). At the maximum sensitivity value of 12 the resulting gain will be di-
vided by 12. For other sensitivities respective gains will be calculated.
Real transducers do not always have sensitivities between 1 and 12. This is accom-
plished by shifting the decimal point. By this means the following input ranges for
transducer sensitivity are obtained:
•0.1000 .. 1.2000 mV/mech. unit
•01.000 .. 12.000 mV/mech. unit
•010.00 .. 120.00 mV/mech. unit
•0100.0 .. 1200.0 mV/mech. unit
•01000 .. 12000 mV/mech. unit
Transducer sensitivity may be entered in different ways:
•Prompt after connecting an IEPE transducer (section 10.2. on page 17)
•Entering a value by the sensitivity menu (section 10.2.5 on page 18)
•Automatic reading of the sensitivity from the memory of a TEDS transducer
(section 10.2.6 on page 18)
•Programming via the interfaces (section 13 on page 35)
If the sensitivity was entered or detected correctly, the display will immediately start
to show values with the selected mechanical units. The amplifier output will provide
the normalized signal.
Entering a transducer sensitivity is only possible for channels where a mechanical
measuring unit was selected (section 10. . on page 20). For the measuring unit mV
or V only the basic gain ranges of 0, 20, 0 and 60 dB (1, 10, 100 and 1000) are
available.
15

10.2.2. Normalization of the Display
The following table shows the full scale values for different transducer sensitivities
and gain ranges for the example of an accelerometer in m/s².
0 dB 20 dB 40 dB 60 dB
0.1 ..
1.0 m /ms-2 **
100.0 ..
10.0 km/s² * 10.00 km/s² 1000 m/s² 100.0 m/s²
1 ..
10 m /ms-2 **
10.00 ..
1.00 km/s² * 1000 m/s² 100.0 m/s² 10.00 m/s²
10 ..
100 m /ms-2 **
1000 ..
100 m/s² * 100.0 m/s² 10.00 m/s² 1.000 m/s²
100 ..
1000 m /ms-2 **
100,0 ..
10.0 m/s² * 10.00 m/s² 1.000 m/s² 100.0 mm/s²
1000 ..
10 000 m /ms-2 **
10,00 ..
1.00 m/s² * 1.000 m/s² 100.0 mm/s² 10.00 mm/s²
* At a gain of 0 dB and the maximum transducer sensitivity value the full-scale
output is limited to 10 % since the input magnitude cannot exceed 10 V.
** For simplification a transducer sensitivity range of 1 to 10 was assumed. At the
actual limits of 1.2 / 12 / 120 / 1200 / 12000 mV/mech. unit the shown full-
scale values must be divided by 1.2.
10.2.3. Normalization of the Amplifier Output
If transducer sensitivities have been entered correctly, the amplifier outputs
(“OUT”) will provide a signal which represents the measured mechanical quantity
as a voltage in multiples of ten. The following table shows the measuring ranges in
mechanical units (m.u.) for different gain settings and transducer sensitivities.
1V at amplifier output equals ...
0 dB 20 dB 40 dB 60 dB
0.1 ..
1.2 m /ms-2 10 000 m.u. 1000 m.u. 100 m.u. 10 m.u.
1 ..
10 m /ms-2 1000 m.u. 100 m.u. 10 m.u. 1 m.u.
10 ..
100 m /ms-2 100 m.u. 10 m.u. 1 m.u. 0.1 m.u.
100 ..
1000 m /ms-2 10 m.u. 1 m.u. 0.1 m.u. 0.01 m.u.
1000 ..
10 000 m /ms-2 1 m.u. 0.1 m.u. 0.01 m.u. 0.001 m.u.
16

The mechanical unit represents m/s² for accelerometers, N for force transducers, Pa
for measuring microphones and kPa for pressure transducers (see also section 10.
on page 20).
10.2.4. Sensor Detection
The M208A automatically detects a connected sensor at its inputs. This detection is
based on the transducer bias voltage (see section 3 on page 7).
Please note:
Sensor detection only functions if display multiplexing is active. Before con-
necting the sensor the display must show: “OK: Stop rot.”. Multiplexing is
started and stopped by the OK key.
Sensors can only be detected if the corresponding channel is active (section
10.3 on page 19).
For sensor detection the IEPE supply of the respective channel must be
switched on (section 12. on page 31).
Please do not connect several sensors at once. Connect them one by one and
wait until each sensor is detected.
Deactivation of unused channels is recommended to avoid interference (section
10.3 on page 19).
When the M208A detects the connection of a new sensor, it will show the message
“New sensor detected” and ask the user to enter the sensitivity. Sensitivity is entered
with five digits and a decimal point in millivolts per mechanical unit. Default value
is the previously entered sensitivity for this channel.
Numbers are entered by the ▲▼keys. Use the ◄ ► keys to change between the
digits. The decimal point is shifted by pressing the GAIN key. Press OK to confirm
the entry.
Only numbers between 1000 and 12000 are accepted, regardless of the decimal
point position. Please shift the decimal point so that the resulting value is in the per-
missible range.
Example: Sensitivity: 92.5 mV/ms-2 → Entry: “092.50”
Sensitivity: 125.56 mV/ms-2 → Entry: “0125.6”
17
Figure 12: Sensor detection and sensi-
tivity entry

Notice: Sensitivities between 1 and 1.2, 10 and 12, 100 and 120 etc. can be en-
tered in two ways.
The example shows this for 1.1 mV/ms-2, 11 mV/ms-2 and 110 mV/ms-2.
Alternative 1: 01.100 / 011.00 / 0110.0 mV/ms-2
Alternative 2: 1.1000 / 11.000 / 110.00 mV/ms-2
The first alternative should be preferred since the total gain of the ampli-
fier will be ten times higher in this case which will improve accuracy.
10.2.5. Entering Transducer Sensitivity in the Menu
Transducer sensitivity may be entered manually via the sensor menu which opens
after pressing the SENSOR key. Select the desired channel using the ▲▼ and OK
keys. Enter the sensitivity as described above.
10.2.6. Automatic Sensitivity Adjustment with TEDS Sensors
The M208A will automatically detect the connection of a TEDS sensor (see section
on page 8) and read out its sensitivity. It will prompt “TEDS Sensor at Ch. ...”,
show TEDS version, template number, model number and, if applicable, the direc-
tion (X/Y/Z).
After pressing OK the display shows the serial number, the measuring ID and the
first 15 letters of the user text stored in the TEDS memory. Sensitivity is shown in
the third line. Press OK to accept this sensitivity or skip normalization by pressing
ESC.
18
Figure 13: Entering transducer sensitiv-
ity
Figure 1 : TEDS detection

If the sensitivity stored in the TEDS memory should exceed the permissible limits
of the M208A (0.1 to 12000 mV/mech. unit), an error message “TEDS sensitivity
out of range” will appear.
Any other parameters stored in the TEDS memory (see section on page 8) will not
be used by the M208A.
The instrument supports the TEDS templates no. 25 for accelerometers and force
transducers and no. 27 for measuring microphones. Other TEDS templates lead to
the error message “TEDS incompatible”.
Erroneous TEDS data will cause the error message “TEDS Checksum error”.
10.3. Channel egistration
The measuring display can be activated separately for each channel. A deactivated
channel is skipped in the multiplexed display mode. New sensors will not be de-
tected for deactivated channels (compare section 10.2. on page 17). For channel
registration press the MENU key and select “ /6: Channel on/off”.
Use the keys ▲▼◄ ► to deactivate (○) or activate (●) the respective channel.
Confirm by OK or quit without changes by ESC.
Channel registration only concerns the display. The respective amplifier channel
will continue to work normally.
 Automatic sensor detection only works for registered channels.
 Deactivate the measuring display of unconnected channels.
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Figure 15: TEDS sensitivity display
Figure 16: Channel registration

10.4. Measuring Unit
The measuring display can show individual measuring units for each channel. The
unit can be electrical (mV / V) or mechanical, depending on the connected sensor:
•m/s² (accelerometer, also for velocity and displacement when using integrators)
•N (force transducer)
•Pa (measuring microphone)
•kPa (pressure transducer)
Open the menu “2/6: Display unit” to select the desired channel or all channels of
the instrument and the measuring unit using the keys ▼▲ and confirm with OK.
After changing the measuring unit, the transducer sensitivity of the respective
channel will be reset to “0.1000”.
If a measuring channel is equipped with an integrator module (section 11 on
page 2 ), the displayed measuring unit will always be µm/s, mm/s or m/s for
single integration and nm, µm or mm for double integration.
If the selected measuring unit is volts, transducer normalization is not possible.
The respective channel works with the basic gain ranges 0, 20, 0 or 60 dB (1,
10, 100 or 1000).
10.5. Display Mode
The M208A can display the amplifier output as true RMS or peak values. Measur-
ing time is 1 s per channel. Open the menu “3/6: Display mode” to choose between
the two modes and press OK to confirm.
The selection is used for all channels.
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Figure 18: Selecting the display mode
Figure 17: Selecting measuring units