MMF KSI84 Series User manual

Instruction Manual
Manfred Weber
Metra Mess- und Frequenztechnik in Radebeul e.K.
Meissner Str. 58 - D-01445 Radebeul
Tel. [phone] Fax [phone]
Email: [e-mail] Internet: www.MMF.de
4-20 mA
Vibration Sensor
Type
KSI84xx
v1.32.030

2
Published by:
Manfred Weber
Metra Mess- und Frequenztechnik in Radebeul e.K.
Meißner Str. 58
D-01445 Radebeul
Tel. [phone]
Fax [phone]
Email [email protected]
Internet www.MMF.de
Note: The latest version of this document can be found at:
https://www.mmf.de/product_literature.htm
All rights reserved, including those of translation.
Subject to modifications.
© 2021 Manfred Weber Metra Mess- und Frequenztechnik in Radebeul e.K.
Edition: 15.11.2021

3
Contents
1Purpose.....................................................................................................4
2Function....................................................................................................4
3Type Selection..........................................................................................5
3.1 Frequency Range (HP, LP).................................................................5
3.2 Measuring Range................................................................................6
3.3 Type Code ..........................................................................................6
4Sensor Operation.....................................................................................7
4.1 Sensor Mounting.................................................................................7
4.2 Sensor Connection .............................................................................7
4.2.1 Connection to the Loop Supply..................................................7
4.2.2 Sensor Cable.............................................................................8
4.2.3 Grounding Concept....................................................................8
4.3 Connection of the Measuring Device..................................................9
4.3.1 Maximum Load Resistance RL...................................................9
4.4 Sensor Self-Test...............................................................................10
4.5 Measuring Mode...............................................................................10
4.5.1 Sensitivity Bi.............................................................................10
4.5.2 Calculation of Acceleration and Velocity..................................10
4.5.3 Offset Current and Noise .........................................................11
4.5.4 Linear Measuring Range xmin…xmax .........................................11
4.5.5 Maximum Dynamic Range.......................................................12
4.6 Overload Display...............................................................................12
4.7 Averaging Filter.................................................................................12
4.7.1 Number of Averages N.............................................................12
4.7.2 Settling Time T.........................................................................13
4.8 Total accuracy...................................................................................13
4.9 Error Messages.................................................................................14
4.9.1 Steps to Fix a LOOP Error.......................................................14
5Technical Data........................................................................................15
5.1 Technical Characteristics of the 4-20mA Signal Conditioning...........15
5.2 Electrical Characteristics...................................................................15
5.3Mechanical Characteristics...............................................................15
5.4 Environmental Characteristics ..........................................................15
5.5 Type Tables......................................................................................16
5.5.1 Acceleration, RMS ...................................................................16
5.5.2 Acceleration, PEAK..................................................................17
5.5.3 Velocity, RMS ..........................................................................18
5.5.4 Velocity, PEAK.........................................................................18
Limited Warranty........................................................................................19
Declaration of Conformity.........................................................................19

4
1 Purpose
The vibration sensors of the KSI84xx family are used to measure vibration
acceleration or velocity on machines and objects.
The sensors measure the vibration amplitude within a specified frequency range in
axial sensor direction and outputs the measuring result as a 4-20 mA current loop
signal. The sensor is supplied with power via the same signal line.
The sensor parameters are adjustable. There are different types for different appli-
cations in several measuring ranges. The sensors comply with the specifications for
vibration measuring devices according to ISO 2954.
Possible applications are:
1. Measurement of the smooth running of rotating machines and
reciprocating machines according to ISO 10816 / ISO 20816.
2. Measurement of bearing vibrations according to VDI 3832.
3. Measurement of vibrations in defined frequency ranges.
The sensors are suitable for use in harsh environmental conditions. The housing is
double shielded, electrically isolated and complies with protection grade IP68.
2 Function
The sensors of the KSI84xx family are piezoelectric vibration sensors.
A piezoelectric accelerometer is used as the sensor element. Its electrical output
signal is first amplified and digitized.
The signal analysis is digital. The signal is filtered (HP, LP), optionally integrated
and the amplitude value is calculated, either as RMS or PEAK value. Finally, the
amplitude value is converted into a 4-20 mA current loop signal with a 16 bit DAC.
Piezo
GAIN
A
D
D
A
+
-
RXD
TXD
Signal
Analysis
4-20mA
KSI84xx
Parameter Set
- Range
- HP Filter, LP Filter
- Integrator
- RMS/Peak
- Average Filter
Port
ERROR
Detection
OVL
Detection
POWER
Supply

5
Either the acceleration (without integration) or the velocity (with integration) of the
vibration can be measured.
In addition, proper sensor function and input signal are monitored. Defects or
overloads are signaled by an error current value.
Before delivery, the sensor is parameterized according to the type code selected by
the customer.
3 Type Selection
There are four different basic types, which differ in the measured quantity
(acceleration or velocity) and the amplitude mode (RMS or PEAK).
Sensor type
KSI84AR-xx
KSI84AP-xx
KSI84VR-xx
KSI84VP-xx
Quantity
Q
Acceleration
Velocity
Mode
M
RMS
PEAK
RMS
PEAK
Furthermore, the types differ in the measured frequency range (HP, LP) and in their
measuring range.
3.1 Frequency Range (HP, LP)
The used frequency range of a sensor type is described by the values HP and LP in
the type table.
HP is the -3 dB cutoff frequency of the high pass filter and determines the lower
cutoff frequency of the sensor.
LP is the -3 dB cutoff frequency of the low pass filter and determines the upper
cutoff frequency of the sensor.
All frequencies between the lower and upper cutoff frequency have an impact to the
measuring result.
Sensors measuring acceleration have a 2nd order IIR high pass and low pass filter
with a stopband attenuation of -40 dB/decade.
Frequency response

6
The HP filter of velocity sensor types has a stopband attenuation of -50 dB/decade,
the LP filter has a stopband attenuation of - 40 dB/decade.
3.2 Measuring Range
The “Range” value in the type table corresponds to the measured value at which the
sensor current is 20 mA. At this level the sensor output is regarded as 100 %.
The measured value must always be within the linear measuring range. This is the
range from 1 % to 112.5 % referred to 20 mA.
3.3 Type Code
The type code is printed on the sensor housing. It is composed according to the
following key. Note that only integer values without decimal places are printed in
the type code.
Range
in m/s² (2…3 places)
in mm/s (2 places)
Low-Pass filter
-3dB cutoff frequency
(2…3 places)
High-Pass filter
-3dB cutoff frequency
(1…3 places)
Mode
R: RMS
P: Peak
Quantity
A: Acceleration
V: Velocity
KSI84QM-HHH-LLL-RRR
Frequency response

7
4 Sensor Operation
4.1 Sensor Mounting
The choice of an appropriate measuring point on the target is important for accurate
vibration measurement. It can be helpful to consult a specialist in machine moni-
toring for this purpose.
In general, it is advisable to measure vibrations as near as possible to their source.
This minimizes errors by transmitting mechanical components.
Suitable measuring points are rigid components, for instance the housing of bearings
or gearboxes. Not recommended for vibration measurement are lightweight, flexible
and soft components. The standard ISO 10816-1 gives some recommendations for
suitable measuring points.
The KSI84xx is mounted via the M8 threaded hole in the sensor base. The sensor
can either be mounted directly using the M8 mounting stud type 043 or with the help
of the mounting pad type 229 with M8 stud by epoxy cementing on the object.
Alternatively, the senor can also be fixed by the magnetic base type 208 (M8) or
type 008 (M5) in combination with the thread adapter type 044.
The sensor should be in touch with the target by its complete mounting surface.
Rough, scratched or too small measuring points may cause errors. Cast or varnish
surfaces are unsuited.
A thin layer of silicone grease between the mounting surfaces also improves
vibration transmission.
4.2 Sensor Connection
4.2.1 Connection to the Loop Supply
The sensor is connected via PIN 2 (+) and PIN 3 (-) of the output connector to the
loop supply voltage. PIN 1 and PIN 4 are not to be connected.
1: Do not connect
2: + current loop
3: - current loop
4: Do not connect
The loop supply voltage USshould be within 10 to 30 V and free of noise.
It is recommended to select a lower voltage at ambient temperatures above 80 °C in
order to reduce self-heating due to the power dissipation inside the sensor.
- Loop
+ Loop
n.c.
3
2
4
1
View at sensor pins
n.c.

8
4.2.2 Sensor Cable
We recommend to use shielded cable for best EMI protection. The cable shield has
be connected to earth potential at one end (see 4.2.3).
Metra offers the following connection accessory:
Type 080G/W: Binder 713, female, straight (G) or angled (W) with screw
terminals for connection an existing sensor cable; protection grade IP67
Type 082-B713G-PIG-x or type 082-B713G-PIG-x:
Shielded sensor cable, x m length with Binder 713, female, straight (G) or
angled (W) and cable end sleeves; protection grade IP67
Make sure that the cable is not routed alongside AC power lines and in adequate
distance to potential EMI sources. It should cross AC power lines at right angles.
4.2.3 Grounding Concept
The sensor has an outer and an inner housing shield to protect the electronics against
EMI. Both housings are electrically isolated from each other.
The inner shield is connected via PIN3 to the potential of thee negative loop line.
The outer sensor housing is direct connected to ground via the M8 mounting thread
(case 1) or is connected via the cable shield (case 2).
Case 1: Direct grounding
Sensor connection with type 080G/W:
Sensor connector electrically isolated
→ connect shield toground on device
side
Sensor connection with type 082-B713G-PIG-x
or type 082-B713W-PIG-x:
Shield connected to sensor connector
→ Leave shield open on device side
Case 2: potential free mounting
Case 2: Isolated mounting
Sensor connection with type 082-B713G-PIG-x
or type 082-B713W-PIG-x:
→ connect shield toground on device
side
Sensor connection with type 082-B713G-PIG-x
or type 082-B713W-PIG-x:
→ connect shield toground on device
side

9
4.3 Connection of the Measuring Device
The following figures show possibilities to measure the sensor current.
The sensor current can be measured either directly by a current meter connected in
series or indirectly by measuring the voltage drop across the load resistance RL
between PIN 3 and the negative terminal.
Choose the connection shown in the first figure for best EMI protection.
The voltage drop uLacross RLis calculated from the sensor current as follows:
  
The following table shows the voltage drop uLas a function of the sensor current at
different load resistors RL.
Voltage drop over RL
Excitation
iSensor
125 
250
500
0 %
4 mA
0,5 V
1 V
2 V
10 %
5,6 mA
0,7 V
1,4 V
2,8 V
20 %
7,2 mA
0,9 V
1,8 V
3,6 V
50 %
12,0 mA
1,5 V
3 V
6 V
100 %
20,0 mA
2,5 V
5 V
10 V
112,5 %
22,0 mA
2,75 V
5,5 V
11 V
4.3.1 Maximum Load Resistance RL
The maximum load resistance RLdepends on the loop supply voltage US. It results
from the fact that the sensor requires at least 7 V at the highest possible loop current.
The calculation is as follows:
 
   󰇛 󰇜 
RL: Load resistance of current loop
US: Loop supply voltage in V
It can be seen that the load resistance RLmust not exceed 680 with a supply
voltage US= 24 V.
KSI84xx
+ PIN 2
- PIN 3
A
+
Us
-
KSI84xx
+ PIN 2
+
- PIN 3
A
Us
-
KSI84xx
+ PIN 2
+
Us
-
- PIN 3
RL
-
V

10
4.4 Sensor Self-Test
The sensor starts with a self-test once it is connected to the loop supply voltage.
During self-test, the sensor outputs the maximum sensor current of 22 mA and the
offset current of 4 mA for a duration of 2 seconds. These currents can be measured
with an ampere meter to ensure proper function.
If there is no error, the normal measuring operation starts afterwards, in which the
sensor current corresponds to the current measured value.
If the sensor is not able to output 22 mA, there is a LOOP error. In this case, the
sensor repeats the self-test until the error is fixed.
4.5 Measuring Mode
4.5.1 Sensitivity Bi
In measuring mode, the sensor output current iSensor is proportional to the vibration
amplitude. A constant offset current of 4 mA is overlaid on this current for the
sensor supply.
            
The proportionality factor Bia or Biv is called sensitivity. The sensitivity depends on
the measuring range of the sensor. It results from the quotient of the current change
at 100 % excitation and the measuring range.
 󰇛  󰇜
  
The following table shows the sensitivity of the acceleration and velocity types for
different measuring ranges.
Range
KSI84Ax
10
20
50
100
200
500
Bia / mA/m/s²
1.6
0.8
0.32
0.16
0.08
0.032
Range
KSI84Vx
10
12.7
20
25.4
40
50.8
Biv / mA/mm/s
1.6
1.26
0.8
0.63
0.4
0.315
The sensitivity Bichanges only slightly over temperature due an electronic
compensation. The remaining TC(Bi) can be found in the technical data.
4.5.2 Calculation of Acceleration and Velocity
The acceleration or velocity is determined from the sensor current as follows:
    

 󰇛  󰇜    
  󰇛  󰇜