KROHNE SU 501 Ex User manual
SU 501 Ex Handbook
Switch Amplier
Controller
2
Contents
SU 501 Ex • Controller
27953-EN-191108
Contents
1 About this document ............................................................................................................... 3
1.1 Function ........................................................................................................................... 3
1.2 Target group ..................................................................................................................... 3
1.3 Symbols used................................................................................................................... 3
2 For your safety ......................................................................................................................... 4
2.1 Authorised personnel ....................................................................................................... 4
2.2 Appropriate use................................................................................................................ 4
2.3 Warning about incorrect use............................................................................................. 4
2.4 General safety instructions............................................................................................... 4
2.5 CE conformity................................................................................................................... 5
2.6 Installation and operation in the USA and Canada ........................................................... 5
2.7 Safety instructions for Ex areas ........................................................................................ 5
3 Product description ................................................................................................................. 6
3.1 Conguration.................................................................................................................... 6
3.2 Principle of operation........................................................................................................ 6
3.3 Adjustment ....................................................................................................................... 7
3.4 Packaging, transport and storage..................................................................................... 7
4 Mounting................................................................................................................................... 8
4.1 General instructions ......................................................................................................... 8
4.2 Mounting instructions ....................................................................................................... 8
5 Connecting to power supply................................................................................................. 11
5.1 Preparing the connection ............................................................................................... 11
5.2 Connection procedure.................................................................................................... 11
5.3 Wiring plan ..................................................................................................................... 12
6 Setup ....................................................................................................................................... 13
6.1 Adjustment system......................................................................................................... 13
6.2 Adjustment elements...................................................................................................... 14
6.3 Function table................................................................................................................. 17
7 Maintenanceandfaultrectication...................................................................................... 19
7.1 Maintenance .................................................................................................................. 19
7.2 Rectify faults................................................................................................................... 19
7.3 How to proceed if a repair is necessary.......................................................................... 21
8 Dismount................................................................................................................................. 22
8.1 Dismounting steps.......................................................................................................... 22
8.2 Disposal ......................................................................................................................... 22
9 Supplement ............................................................................................................................ 23
9.1 Technical data ................................................................................................................ 23
9.2 Dimensions .................................................................................................................... 25
9.3 Trademark ...................................................................................................................... 26
Editing status: 2019-11-08
3
1 About this document
SU 501 Ex • Controller
27953-EN-191108
1 About this document
1.1 Function
This instruction provides all the information you need for mounting,
connection and setup as well as important instructions for mainte-
nance,faultrectication,theexchangeofpartsandthesafetyofthe
user. Please read this information before putting the instrument into
operation and keep this manual accessible in the immediate vicinity
of the device.
1.2 Target group
This operating instructions manual is directed to trained personnel.
Thecontentsofthismanualmustbemadeavailabletothequalied
personnel and implemented.
1.3 Symbols used
Information, note, tip: This symbol indicates helpful additional infor-
mation and tips for successful work.
Note: This symbol indicates notes to prevent failures, malfunctions,
damage to devices or plants.
Caution: Non-observance of the information marked with this symbol
may result in personal injury.
Warning: Non-observance of the information marked with this symbol
may result in serious or fatal personal injury.
Danger: Non-observance of the information marked with this symbol
results in serious or fatal personal injury.
Ex applications
This symbol indicates special instructions for Ex applications.
• List
The dot set in front indicates a list with no implied sequence.
1 Sequence of actions
Numbers set in front indicate successive steps in a procedure.
Battery disposal
This symbol indicates special information about the disposal of bat-
teries and accumulators.
4
2 For your safety
SU 501 Ex • Controller
27953-EN-191108
2 For your safety
2.1 Authorised personnel
All operations described in this documentation must be carried out
onlybytrained,qualiedpersonnelauthorisedbytheplantoperator.
During work on and with the device, the required personal protective
equipment must always be worn.
2.2 Appropriate use
SU 501 Ex is a universal controller for connection of level switches.
Youcannddetailedinformationabouttheareaofapplicationin
chapter "Product description".
Operational reliability is ensured only if the instrument is properly
usedaccordingtothespecicationsintheoperatinginstructions
manual as well as possible supplementary instructions.
2.3 Warning about incorrect use
Inappropriate or incorrect use of this product can give rise to applica-
tion-specichazards,e.g.vesseloverllthroughincorrectmounting
or adjustment. Damage to property and persons or environmental
contamination can result. Also, the protective characteristics of the
instrument can be impaired.
2.4 General safety instructions
This is a state-of-the-art instrument complying with all prevailing
regulations and directives. The instrument must only be operated in a
technicallyawlessandreliablecondition.Theoperatorisresponsi-
ble for the trouble-free operation of the instrument. When measuring
aggressive or corrosive media that can cause a dangerous situation
if the instrument malfunctions, the operator has to implement suitable
measures to make sure the instrument is functioning properly.
During the entire duration of use, the user is obliged to determine the
compliance of the necessary occupational safety measures with the
current valid rules and regulations and also take note of new regula-
tions.
The safety instructions in this operating instructions manual, the na-
tional installation standards as well as the valid safety regulations and
accident prevention rules must be observed by the user.
For safety and warranty reasons, any invasive work on the device
beyond that described in the operating instructions manual may be
carried out only by personnel authorised by the manufacturer. Arbi-
traryconversionsormodicationsareexplicitlyforbidden.Forsafety
reasons,onlytheaccessoryspeciedbythemanufacturermustbe
used.
To avoid any danger, the safety approval markings and safety tips on
the device must also be observed and their meaning read in this oper-
ating instructions manual.
5
2 For your safety
SU 501 Ex • Controller
27953-EN-191108
2.5 CE conformity
ThedevicefullsthelegalrequirementsoftheapplicableEUdirec-
tives.ByaxingtheCEmarking,weconrmsuccessfultestingofthe
product.
2.6 Installation and operation in the USA and
Canada
This information is only valid for USA and Canada. Hence the follow-
ing text is only available in the English language.
Installations in the US shall comply with the relevant requirements of
the National Electrical Code (ANSI/NFPA 70).
Installations in Canada shall comply with the relevant requirements of
the Canadian Electrical Code.
2.7 Safety instructions for Ex areas
For Ex applications, only devices with corresponding Ex approval may
beused.ObservetheEx-specicsafetyinstructions.Thesearean
integral part of the operating instructions and are enclosed with every
device with Ex approval.
6
3 Product description
SU 501 Ex • Controller
27953-EN-191108
3 Product description
3.1 Conguration
The scope of delivery encompasses:
• Controller SU 501 Ex
• Terminal socket
• Bridges (4 pieces)
• Coding pins (2x)
• Ex label
• Ex separating chamber
• Documentation
– This operating instructions manual
– Ex-specic"Safety instructions" (with Ex versions)
– Ifnecessary,furthercerticates
The SU 501 Ex consists of:
• Controller SU 501 Ex
56 78
910121314
TEST
on
3
1
2
Fig. 1: SU 501 Ex
1 Ex separating chamber with Ex version
2 Terminal socket
3 Transparent cover
Thetypelabelcontainsthemostimportantdataforidenticationand
use of the instrument:
• Article number
• Serial number
• Technical data
• Article numbers, documentation
3.2 Principle of operation
SU 501 Ex is a single controller for processing of vibrating level
switches.
Scope of delivery
Constituent parts
Type label
Application area
7
3 Product description
SU 501 Ex • Controller
27953-EN-191108
The SU 501 Ex controller powers connected sensors and simultane-
ously processes their measuring signals.
When the medium reaches the switching point of the sensor, the sen-
sor current changes.This is measured and evaluated by SU 501 Ex.
The change causes the output relays to switch according to the set
operating mode.
Wide range power supply unit with 20 … 253 V AC/DC for worldwide
use.
Detailed information about the power supply can be found in chapter
"Technical data".
3.3 Adjustment
All adjustment elements are located under a hinged front cover. The
operating mode and the switching delay can be set via a DIL switch
block. In addition, the correct function of the measuring system can
be checked with a test key.
3.4 Packaging, transport and storage
Your instrument was protected by packaging during transport. Its
capacity to handle normal loads during transport is assured by a test
based on ISO 4180.
The packaging of standard instruments consists of environment-
friendly, recyclable cardboard. For special versions, PE foam or PE
foil is also used. Dispose of the packaging material via specialised
recycling companies.
Transport must be carried out in due consideration of the notes on the
transport packaging. Nonobservance of these instructions can cause
damage to the device.
The delivery must be checked for completeness and possible transit
damage immediately at receipt. Ascertained transit damage or con-
cealed defects must be appropriately dealt with.
Up to the time of installation, the packages must be left closed and
stored according to the orientation and storage markings on the
outside.
Unless otherwise indicated, the packages must be stored only under
the following conditions:
• Not in the open
• Dry and dust free
• Not exposed to corrosive media
• Protected against solar radiation
• Avoiding mechanical shock and vibration
• Storage and transport temperature see chapter "Supplement -
Technical data - Ambient conditions"
• Relative humidity 20 … 85 %
Functional principle
Voltage supply
Packaging
Transport
Transport inspection
Storage
Storage and transport
temperature
8
4 Mounting
SU 501 Ex • Controller
27953-EN-191108
4 Mounting
4.1 General instructions
SU 501 Ex controller with plug-in socket for mounting on carrier rail
according to EN 50022.
The front plate of SU 501 Ex can be provided with a lead-sealable
transparent cover to protect the instrument against unauthorised or
inadvertentadjustment.Seethefollowinggureonhowtoremovethe
transparent cover.
Fig. 2: Removing the transparent cover
For moisture-protected mounting outside the switching cabinet, we
oeraninsulatedprotectivehousingwithtransparentcover(IP65)for
surface mounting.
In this housing you can mount a maximum of 3 instruments of 36 mm
width.
4.2 Mounting instructions
The plug-in socket is constructed for carrier rail mounting according to
EN 50022. Operating voltage is connected to terminals 9 and 10. For
neighbouring controllers, it is possible to continue connection L1 and
N directly via the supplied bridges.
Danger:
The bridges must never be used with single instruments or at the end
of a row of instruments. If this rule is not heeded, there is a danger
of coming into contact with the operating voltage or causing a short
circuit.
A SU 501 Ex in Ex version is an auxiliary, intrinsically safe instrument
and may not be installed in explosion-endangered areas.
Installation location
Transparent cover
Housing IP65
Installation
9
4 Mounting
SU 501 Ex • Controller
27953-EN-191108
Before setup, the Ex separating chamber must be attached (as shown
below) with Ex versions. Safe operation can be only ensured if the
operatinginstructionsmanualandtheEGtypeapprovalcerticate
are observed. SU 501 Ex must not be opened.
Close the upper terminals according to the following illustration.
12 43
Fig. 3: Mounting the separating chamber
Allcontrollersareprovidedwithdierentgapsdependingontypeand
version (mechanical coding).
The plug-in socket is provided with coded pins that can be inserted to
prevent accidental interchanging of the various instrument types.
With a SU 501 Ex in Ex version, the supplied coded pins (type coded
pin and Ex coded pin) must be inserted by the user according to the
below table.
Ex separating chamber
Instrument coding
10
4 Mounting
SU 501 Ex • Controller
27953-EN-191108
Typ 600-1
56 78
141312109
4321
EEx ia
+
-
L1
N
DISBUS
0...10V
9
8
7
3
2
1
C
B
A
12
Plug-in socket
2
1
3
4
Fig. 4: Plug-in socket SU 501 Ex
1 Bridges for looping the operating voltage
2 Type coding for SU 501 Ex
3 Ex coding with Ex version
4 Ex separating chamber
11
5 Connecting to power supply
SU 501 Ex • Controller
27953-EN-191108
5 Connecting to power supply
5.1 Preparing the connection
Always keep in mind the following safety instructions:
• Connect only in the complete absence of line voltage
• If overvoltage surges are expected, overvoltage arresters should
be installed.
Inhazardousareasyoumusttakenoteoftherespectiveregulations,
conformityandtypeapprovalcerticatesofthesensorsandpower
supply units.
Thepowersupplycanbe20…250VAC,50/60Hzor20…72VDC.
The voltage supply of SU 501 Ex is connected with standard cable
according to the national installation standards.
The sensors are connected with standard two-wire cable without
screen. If electromagnetic interference is expected which is above the
test values of EN 61326 for industrial areas, screened cable should
be used.
Use cable with round cross-section. A cable outer diameter of
5…9mm(0.2…0.35in)ensuresthesealeectofthecablegland.
Ifyouareusingcablewithadierentdiameterorcross-section,
exchange the seal or use a suitable cable gland.
Connect the cable screen on both ends to ground potential. In the
sensor, the screen must be connected directly to the internal ground
terminal. The ground terminal on the outside of the sensor housing
must be connected to the potential equalisation (low impedance).
If potential equalisation currents are expected, the screen connec-
tion on SU 501 Ex must be made via a ceramic capacitor (e. g. 1 nF,
1500 V). The low frequency potential equalisation currents are thus
suppressed,buttheprotectiveeectagainsthighfrequencyinterfer-
ence signals remains.
Take note of the corresponding installation regulations for Ex applica-
tions. In particular, make sure that no potential equalisation currents
owoverthecablescreen.Incaseofgroundingonbothsidesthis
can be achieved by the use of a capacitor or a separate potential
equalisation.
5.2 Connection procedure
Move on to electrical connection and proceed as follows:
1. Snap the socket without SU 501 Ex onto the carrier rail
2. Connect sensor cable to terminal 1 and 2, and where applicable,
connect the screen
3. Connectpowersupply(switchedo)toterminal9and10
4. Insert SU 501 Ex into the plug-in socket and screw it down tightly
Theelectricalconnectionisnished.
Note safety instructions
Take note of safety
instructions for Ex
applications
Voltage supply
Connection cable
Cable screening and
grounding
Connection cable
for Ex applications
12
5 Connecting to power supply
SU 501 Ex • Controller
27953-EN-191108
Before setting up Ex versions, make sure the Ex separating chamber
is plugged (above the sensor terminals). The pins for type and Ex
coding must also be inserted correctly.
5.3 Wiring plan
3
5 4
1
2
56 78
12 34
910121314
+-
+
L1 N
-
Fig. 5: Wiring plan SU 501 Ex
1 Sensor
2 Sensor input
3 Transistor output
4 Relay output
5 Voltage supply
13
6 Setup
SU 501 Ex • Controller
27953-EN-191108
6 Setup
6.1 Adjustment system
Typ 600-1
on
56 78
910121314
56 78
141312109
4321
TEST
EEx ia
+
-
L1
N
DISBUS
0...10V
9
8
7
3
2
1
C
B
A
12
Plug-in socket
6
5
10
7
7
8
9
1
2
3
4
Fig. 6: Display and adjustment elements
1 Test key
2 Control lamp - level relay (LED yellow)
3 Control lamp - Fault signal (LED red)
4 Control lamp - Operating voltage (LED green)
5 Ex separating chamber
6 Terminal for probe
7 Sockets for bridges
8 Transistor output
9 Relay output
10 Voltage supply
14
6 Setup
SU 501 Ex • Controller
27953-EN-191108
123456
12
6
2
ze
za
AB
off
t sec
IP 30
Sensorstromkreis EEx ia IIC
60mA
-
+
-
+
PTB-Nr.: Ex-95/xxxx X
max: 36V
56
nsp.I
a: -20...+60°C
power supply
20...72VDC
2 W
20...250 VAC
LN
Sensor
12
Terminal
1312
out
14
3AAC/1ADC
500VA/54W
max.250VAC/DC
910
+-
Uo< xx VL
o< xx mH
Co < xx nF
Po< xx mW
Io< xx mA
1
23
Fig. 7: Display and adjustment elements
1 DIL switch block
2 Type label
3 Transparent cover
6.2 Adjustment elements
Control lamps (LED) in the front plate indicate operation, switching
status and fault signal.
• Green
– Operating control lamp
– Mains voltage on, instrument is operating
• Red
– Fault indicator
– Fault on the sensor circuit due to sensor failure or line break
– The relay deenergises in case of failure
• Yellow
Control lamps
15
6 Setup
SU 501 Ex • Controller
27953-EN-191108
– Relay control lamp
– The yellow relay control lamp reacts depending on the set
mode (A/B)
– The relay control lamp generally indicates the activated (ener-
gized)conditionoftherelay
– A dark relay control lamp means that the relay is deenergised
(transistor blocks)
Laterally on top (covered when mounted) there is a DIL switch block
with six switches. The individual switches are assigned as follows:
• 1 - A/B mode
– A-Max.detectionoroverowprotection
– B - Min. detection or dry run detection
• 2-Switchodelay(za)
• 3-Switchondelay(ze)
• 4 - Switching delay 2 s
• 5 - Switching delay 6 s
• 6 - Switching delay 12 s
Withswitch1youcanadjustthemode(A-overllprotectionorB-
dry run protection).
Withswitches2and3youcansetswitchoand/orswitchondelays
independent of each other.
The delay refers to the switching function of the relay.
In the example (see previous illustration), mode A (max. detection of
overllprotection)isselected(switch1).Theswitchodelayisacti-
vated (switch 2) and the switching delay is set to 8 seconds (switch 4,
5 and 6).
With switches 4, 5 and 6 you can adjust the switching delay. The times
oftheactivatedtimeswitchesaccumulate.Iftheswitchon(ze)and
switchodelay(za)areswitchedontogether,thesettimeappliesto
both delay modes.
Hence the relay deenergises with 8 seconds delay time when the
switching point is reached.
Information:
Keep in mind that the switching delay of the sensor and controller
accumulate.
Switch 1 2 3 4 5 6
Time za ze 2 s 6 s 12 s
0.2 s A/B o o o o o
0.5 s A/B 1) o o o
2 s A/B on o o
6 s A/B o on o
8 s A/B on on o
DIL switch block
1) Set alternately switch 2 and/or 3 to "on".The times apply to the adjusted
delay mode.
16
6 Setup
SU 501 Ex • Controller
27953-EN-191108
Switch 1 2 3 4 5 6
Time za ze 2 s 6 s 12 s
12 s A/B o o on
14 s A/B on o on
18 s A/B o on on
20 s A/B on on on
The measuring system is continuously monitored. The following
criteria are checked:
• Line break and shortcircuit (two-wire cable)
• Interruptionoftheconnectioncabletothepiezoelements
• Corrosion or damage on the tuning fork (vibrating rod)
• Break of the tuning fork (vibrating rod)
• Loss of vibration
• Too low vibrating frequency
• Medium penetration into the sensor (from inside vessel)
In systems with OPTISWITCH level switches in conjunction with a
two-wire electronics module, a function test can be carried out. SU
501 Ex has an integrated test key. The test key is lowered in the front
plate of the controller. Push the test key with a suitable object (screw-
driver, pen etc.).
By pushing the key, the system is checked on the following criteria:
• Switching function of the switching outputs
• Potential separation of the outputs
• The signal processing of the controller
After pushing the test key, the complete measuring system is checked
on correct function. The following operating conditions are simulated
during the test:
• Fault message
• Empty signal
• Full signal
Check if all three switching conditions occur in the correct sequence
and the stated duration. If not, there is a fault in the measuring system
(see chapter "Fault rectication").
Note:
Keep in mind that downstream connected devices are activated dur-
ing the function test. This allows you to check the correct function of
the measuring system.
After releasing the key.
A-mode B-mode
1Simulation of a fault signal (approx. 3 s)
Level relay deenergised
Relaycontrollampo Relaycontrollampo
Function monitoring
Test key
Test procedure
17
6 Setup
SU 501 Ex • Controller
27953-EN-191108
A-mode B-mode
1Simulation of a fault signal
Fault indicator
Failure lamp lights Failure lamp lights
2Simulation an empty signal (approx. 1.5 s)
Level relay energised
Relay control lamp
lights
Relaycontrollampo
2Simulation of an empty signal
Fault indicator
Failurelampo Failurelampo
3Simulation of a full signal (approx. 1.5 s)
Level relay deenergised
Relaycontrollampo Relay control lamp
lights
3Simulation of a full signal
Fault indicator
Failurelampo Failurelampo
4Return to the current operating condition (covered/uncov-
ered)
Check the procedure of the function test. Note the following criteria for
assessment of the result:
Test passed
If all three switching conditions occur in the correct sequence and the
speciedduration,thenthetestispassedandtheinstrumentfunc-
tions correctly.
Test not passed
• Thespeciedtimesdeviateconsiderablyfromthetable(>3s)
• One of the switching conditions remains unchanged
• No start-up of the test - no signal sequence
6.3 Function table
The following table provides an overview of the switching conditions
depending on the set mode and the level.
The mode switch on the sensor (if available) must be set to max.
operation.
Sensor (max. operation) Controller
Mode on the
controller
Level Signal current -
Sensor
Signal lamp
- Switching out-
put (yellow)
Control lamp -
Failure (red)
Outputs
Mode A
Overowpro-
tection
approx. 8 mA Relayenergized
transistor con-
ducts
Mode A
Overowpro-
tection
approx. 16 mA Relay deener-
gized
transistor blocks
Evaluation
18
6 Setup
SU 501 Ex • Controller
27953-EN-191108
Sensor (max. operation) Controller
Mode on the
controller
Level Signal current -
Sensor
Signal lamp
- Switching out-
put (yellow)
Control lamp -
Failure (red)
Outputs
Mode B
Dry run protec-
tion
approx. 16 mA Relayenergized
transistor con-
ducts
Mode B
Dry run protec-
tion
approx. 8 mA Relay deener-
gized
transistor blocks
Fault message
(mode A/B)
any approx. 1.8 mA Relay deener-
gized
transistor blocks
19
7Maintenanceandfaultrectication
SU 501 Ex • Controller
27953-EN-191108
7 Maintenanceandfaultrectication
7.1 Maintenance
If the device is used properly, no special maintenance is required in
normal operation.
The cleaning helps that the type label and markings on the instrument
are visible.
Take note of the following:
• Use only cleaning agents which do not corrode the housings, type
label and seals
• Use only cleaning methods corresponding to the housing protec-
tion rating
7.2 Rectify faults
The operator of the system is responsible for taking suitable meas-
ures to rectify faults.
Thedeviceoersmaximumreliability.Nevertheless,faultscanoccur
during operation. These may be caused by the following, e.g.:
• Measured value from sensor not correct
• Voltage supply
• Interference in the cables
Therstmeasuretobetakenistochecktheinputandoutputsignals.
The procedure is described as follows. In many cases the causes can
bedeterminedthiswayandfaultscanbeeasilyrectied.
Error Cause Rectication
The red failure control
lamp (LED) of the control-
ler lights
Sensor not connected cor-
rectly
In Ex systems, make sure that the Ex protection is not
inuencedbythemeasuringinstrumentsused.
Measure the current value on the signal cable to the
sensor
Faults in the sensor causing a current change to below
3.7 mA or over 21 mA lead to a fault signal in the con-
trollers
Sensor not connected cor-
rectly
In Ex systems, make sure that the Ex protection is not
inuencedbythemeasuringinstrumentsused.
Measure the voltage on the connection cable
The terminal voltage of the sensor is at least 12 V in
normal condition
Maintenance
Cleaning
Reaction when malfunc-
tion occurs
Causes of malfunction
Faultrectication
Fault
20
7Maintenanceandfaultrectication
SU 501 Ex • Controller
27953-EN-191108
Error Cause Rectication
The red failure control
lamp (LED) of the control-
ler lights
Currentvalue≤3.7mA Measure the current value on the signal cable to the
sensor
Check all connections and connection cables to the
sensor
The voltage should be approx. 17 … 20 V
If the value is below 17 V, probably the controller is de-
fective.
Exchange the controller or send it in for repair
If the red failure lamp continues to light, separate the
sensor from the connection cable and connect a resis-
torof1kΩinsteadonthecontroller
If the failure lamp continues to light, the controller is de-
fective
Exchange the controller or send it in for repair
Should the failure lamp extinguish, you can connect the
sensor again. Separate the controller from the connec-
tioncableandconnectaresistorof1kΩtothesensor
input
If the failure lamp continues to light, the connection ca-
ble is probably interrupted
Check the connection cable to the sensor
Should the failure lamp extinguish, the sensor will be
defective
Exchange the sensor or send it in for repair
The red failure control
lamp (LED) of the control-
ler lights
Currentvalue≥21mA Measure the current value on the signal cable to the
sensor
Check all connections and connection cables to the
sensor
If the red failure lamp continues to light, separate the
sensor from the connection cable and connect a resis-
torof1kΩinsteadonthecontroller
If the failure lamp extinguishes, the sensor is defective.
Check the connected sensor
If the failure lamp continues to light, connect the sensor
again. Separate controller from the connection cable
andconnectaresistorof1kΩtothesensorinput.
If the failure lamp extinguishes, this is probably due to a
shortcircuit in the connection cable
Check the connection cable to the sensor
If the failure lamp continues to light, the controller is de-
fective
Exchange the controller or send it in for repair
Malfunction during func-
tion test
After pushing the test key,
the switching conditions
do not occur in the correct
sequence or correct dura-
tion, e.g. no full signal is
output.
Measure the line resistance
If the cable is highly resistive, bring it to a normal resist-
ance, e.g. check terminals and cable connections on
corrosion
Other manuals for SU 501 Ex
2
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