Bender ISOMETER iso175 User manual

Manual EN
ISOMETER® iso175
Insulation monitoring device for unearthed drive systems (IT systems) in road
vehicles
iso175_D00415_01_M_XXEN/11.2023

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ISOMETER® iso175
Table of contents
1General information...........................................................................................5
1.1 How to use the manual.................................................................................................................................5
1.2 Indication of important instructions and information.......................................................................5
1.3 Signs and symbols...........................................................................................................................................5
1.4 Service and Support....................................................................................................................................... 5
1.5 Training courses and seminars...................................................................................................................6
1.6 Delivery conditions......................................................................................................................................... 6
1.7 Inspection, transport and storage.............................................................................................................6
1.8 Warranty and liability.....................................................................................................................................6
1.9 Disposal of Bender devices..........................................................................................................................7
1.1 Safety.................................................................................................................................................................... 7
2List of abbreviations.......................................................................................... 8
Device-specific safety instructions................................................................... 9
4Function.............................................................................................................11
4.1 Intended use................................................................................................................................................... 11
4.2 Device features...............................................................................................................................................11
4.3 Funktional description................................................................................................................................ 11
4.3.1 Insulation resistance measurement....................................................................................................... 11
4.3.2 Measured value quality...............................................................................................................................12
4.3.3 Partial resistances RF+ (R_iso_pos) and RF- (R_iso_neg)..................................................................12
4.3.4 Fast start measurement..............................................................................................................................13
4.4 Self test..............................................................................................................................................................14
4.4.1 Online self test............................................................................................................................................... 14
4.4.2 Offline self test............................................................................................................................................... 15
4.4.3 Offline and communication self test..................................................................................................... 15
4.4.4 Periodical / automatic self test.................................................................................................................15
4.5 Measurement profiles..................................................................................................................................16
4.5.1 Available measurement profiles..............................................................................................................16
4.6 Chassis-ground connection.......................................................................................................................17
4.7 Unbalance measurement...........................................................................................................................17
4.8 Measuring the system leakage capacitance....................................................................................... 18
4.9 Voltage measurement.................................................................................................................................18
4.1 Monitoring functions...................................................................................................................................18
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Table of contents
4.1 .1 Device error..................................................................................................................................................... 18
4.1 .2 HV system.........................................................................................................................................................18
4.1 .3 Status output OKHS.......................................................................................................................................2
5Dimensions and mounting.............................................................................. 21
6Wiring................................................................................................................ 22
7Commissioning................................................................................................. 2
8Operation.......................................................................................................... 24
8.1 R_iso_corrected / R_iso_original............................................................................................................. 24
8.2 Interfaces.......................................................................................................................................................... 24
8.2.1 Status output OKHS.......................................................................................................................................24
8.2.2 High-Speed CAN............................................................................................................................................24
8.3 Insulation measurement.............................................................................................................................25
8.4 Checking the connection of the device............................................................................................... 25
8.5 Profile selection..............................................................................................................................................25
9Maintenance and trouble-shooting................................................................27
9.1 Unsafe to start is always active................................................................................................................27
9.2 Insulation measurement.............................................................................................................................27
10 Technical data...................................................................................................29
1 .1 Factory settings..............................................................................................................................................29
1 .2 Tabular data.................................................................................................................................................... 29
1 .3 Standards and approvals............................................................................................................................33
1 .4 Ordering information...................................................................................................................................33
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ISOMETER® iso175
1 General information
1.1 How to use the manual
ADVICE
This manual is intended for qualified personnel working in electrical engineering and electronics!
Part of the device documentation in addition to this manual is the enclosed supplement ‘Safety
instructions for Bender products’.
ADVICE
Read the operating manual before mounting, connecting and commissioning the device. Keep the
manual within easy reach for future reference.
1.2 Indication of important instructions and information
DANGER
Indicates a high risk of danger that will result in death or serious injury if not avoided.
WARNING
Indicates a medium risk of danger that can lead to death or serious injury if not avoided.
CAUTION
Indicates a low-level risk that can result in minor or moderate injury or damage to property if not
avoided.
ADVICE
Indicates important facts that do not result in immediate injuries. They can lead to malfunctions if the
device is handled incorrectly.
Information can help to optimise the use of the product.
1. Signs and symbols
Disposal Protect from moisture Protect from dust
Temperature range Recycling RoHS directives
1.4 Service and Support
Information and contact details about customer service, repair service or field service for Bender devices are
available on the following website: Fast assistance | Bender GmbH & Co. KG.
iso175_D 415_ 1_M_XXEN/11.2 23 5

General information
1.5 Training courses and seminars
Regular face-to-face or online seminars for customers and other interested parties:
www.bender.de > know-how > seminars.
1.6 Delivery conditions
The conditions of sale and delivery set out by Bender GmbH & Co. KG apply. These can be obtained in printed
or electronic format.
The following applies to software products:
Die Elektroindustrie
‘Software clause in respect of the licensing of standard software as part of deliveries,
modifications and changes to general delivery conditions for products and services in the
electrical industry’
1.7 Inspection, transport and storage
Check the shipping and device packaging for transport damage and scope of delivery. In the event of
complaints, the company must be notified immediately, see ‘www.bender.de > service & support.’.
The following must be observed when storing the devices:
1.8 Warranty and liability
Warranty and liability claims for personal injury and property damage are excluded in the case of:
•Improper use of the device.
•Incorrect mounting, commissioning, operation and maintenance of the device.
•Failure to observe the instructions in this operating manual regarding transport, commissioning, operation
and maintenance of the device.
•Unauthorised changes to the device made by parties other than the manufacturer.
•Non-observance of technical data.
•Repairs carried out incorrectly.
•The use of accessories or spare parts that are not provided, approved or recommended by the
manufacturer.
•Catastrophes caused by external influences and force majeure.
•Mounting and installation with device combinations not approved or recommended by the manufacturer.
This operating manual and the enclosed safety instructions must be observed by all persons working with the
device. Furthermore, the rules and regulations that apply for accident prevention at the place of use must be
observed.
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ISOMETER® iso175
1.9 Disposal of Bender devices
Abide by the national regulations and laws governing the disposal of this device.
For more information on the disposal of Bender devices, refer to
www.bender.de > service & support.
1.10 Safety
If the device is used outside the Federal Republic of Germany, the applicable local standards and regulations
must be complied with. In Europe, the European standard EN 5 11 applies.
DANGER Risk of fatal injury due to electric shock!
Touching live parts of the system carries the risk of:
•Risk of electrocution due to electric shock
•Damage to the electrical installation
•Destruction of the device
Before installing the device and before working on its connections, make sure that the installation
has been de-energised. The rules for working on electrical systems must be observed.
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List of abbreviations
2 List of abbreviations
Abbreviation Description
HV High voltage
HS-CAN High speed CAN
Kl. 15 Terminal 15
Kl. 31 Terminal 31
n.c. not connected
OKHS igital status output (LV pin 8, high-side active)
SNV Signal not valid
tbd to be defined
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ISOMETER® iso175
Device-specific safety instructions
DANGER High voltage
Danger to life
The ISOMETER® is galvanically connected to the HV busbar of the vehicle. When it is installed, up to
1 V are applied to the electronic contacts of the HV+ connector and the adjacent components.
This applies also to the switched-off condition, i.e. when the device is not connected to the 12V /
24V voltage supply! The HV+ connector at the device is therefore furnished with a warning (see
below). In addition to the general safety instructions (see chapter “General information”, page 5),
it must also be ensured that prior to the installation and always when working on the connections
of the device (see chapter “Wiring”, page 22), the HV connections are safely disconnected and
reconnecting them is made impossible for the duration of the work.
The system integrator is responsible for the safety of the entire system. He must ensure that there is
sufficient protection against accidental contact according to IEC 61 1 during the normal operation
of the device.
WARNING
Fire hazard
The device is equipped with short-circuit proof inputs. To protect the vehicle’s electric system in the
event of a fault, customers must provide a corresponding back-up fuse or miniature circuit breaker in
the electric circuit of the device's voltage supply.
ADVICE
Make sure when integrating the device that the function of the device cannot be impaired by
condensation or corrosion.
ADVICE
When the energy storage device / battery is charged (e. g. at a charging station), care must be taken
that not more than one isometer (e. g. on the vehicle side and on the charging station) is active at the
same time in order to prevent devices from influencing each other. These devices can disconnect the
connection to chassis ground with a corresponding control command.
ADVICE
Where IT systems are to be galvanically connected, this connection must be ensured by a low ohmic-
resistance connection. Intrinsic diodes, such as body diodes of MOSFET transistors for instance, can
adversely affect the insulations resistance measured value so that the specified tolerances can no
longer be met.
ADVICE
When the periodic self test is deactivated (see chapter “Periodical / automatic self test”, page 15),
the user must verify that the HV system is connected properly by a different method (e. g. by
analysing the high voltage or similar methods).
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Device-specific safety instructions
ADVICE
As prerequisite for proper monitoring of the chassis ground connection (see chapter “Online self
test”, page 14), terminal 31 must be connected to the same potential as LV-pin 3. This connection
may not be made directly at the device itself but via chassis ground. Only in this manner can it be
ensured that LV-pin 3 is also connected to chassis ground.
ADVICE
The ISOMETER® may not be connected to a CAN bus that is critical to safety.
ADVICE
In the event of an insulation fault in the monitored system the connection path of the device will get
hot. That behaviour is normal and must be taken into account when dismounting the device and
searching for faults, especially when ambient temperatures are high.
The internal flash memory guarantees up to 0.000 parameter changes over the entire service life of the
device.
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ISOMETER® iso175
4 Function
4.1 Intended use
The ISOMETER® iso175 product line, called ISOMETER® in the following, is designed for installation in
correspondingly marked HV-components of road vehicles. There it continuously monitors the insulation
resistance of the HV system. Depending on the variant, the device communicates with a higher-level location
using different CAN protocols (standard Bender, SAEJ1939).
Other installation locations in the vehicle or in industry sectors such as e. g. the shipping, railroad or
aerospace industries are considered non-compliant with the intended use.
4.2 Device features
•Suitable for 12V and 24V DC systems (supply voltage)
•Insulation monitoring of DC insulation faults for unearthed systems (IT systems) DC …1 V
•Continuous insulation resistance measurement RF_corrected = …35 MΩ (RF_ original = …5 MΩ)
•Response time ≤3 s for insulation resistances ≤5 Ω/Volt and system leakage capacitances ≤2µF
•Insulation measurement for system leakage capacitances up to 1 µF can be configured by setting
parameters in the high capacitance (“High Capacity“) profile.
•Insulation measurement also when the vehicle's HV electric system is not energised
•Intetrated self diagnosis (online self test)
•HV connection monitoring (offline self test)
•Continuous monitoring of the earth connection
•Undervoltage detection
•Earth connection can be disconnected
•Interfaces:
– Digital output for device error message (OKHS)
•HS-CAN interface with the following protocols
- Bender CAN
- CAN-SAE J1939
– All outputs short-circuit proof
•Load-dump protection up to 58V
4. Funktional description
4. .1 Insulation resistance measurement
The overall insulation resistance measurement of an HV system is based on the patented active AMP
measuring principle. This method uses a measuring voltage source internal to the device that injects a current
into the system to be measured, and the resulting voltage drop is measured. This is carried out independently
of the voltage of the system to be monitored so that the insulation measurement can also be carried out when
the HV system is deenergised.
The measuring duration for an individual measurement generally depends on the following factors and it can
take up to 6 seconds:
•Overall insulation resistance of the HV system
•System leakage capacitance
•Measuring profile used (device parameter)
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Function
The present duration of an individual insulation measurement is output by the measured value Isolation:
Time_elapsed_since_last_measurement. At the beginning of each new insulation measurement this value is
automatically reset to s.
Due to the then following internal statistical filtering and averaging of the individual measured values, the
insulation resistance measured value is only available at the device interface with a delay (after up to 12
individual measurements).
When the fast start measurement is activated (Power-On profile “Standard with fast startup” or “High Capacity
with fast startup”), the insulation resistance measured values (R_iso_original, R_iso_corrected and R_iso_neg,
R_iso_pos) satisfy the specified tolerance as soon as the status signals R_iso_status = 0xFE.
When the fast start measurement is deactivated (Power-On profile “Standard”, “High Capacity”, “Disturbed”,
“Service"), the specified tolerance is met only after 12 individual measured values have been obtained in the
status R_iso_status = 0xFE.
For a rough estimate of the duration of an individual measurement, the following approximation formula
can be used:
t ~ 5 * Ri II Riso * Ce
An insulation resistance R_iso_corrected is made available at the interface, and from which the currently
valid “tolerance value“ (set tolerance percentage times measured value) is subtracted. This ensures that this
measured value never exceeds the actually present insulation resistance. The following example serves to
illustrate this device function:
Rf = 1MΩ, R_iso_original (measured) = e.g. 1. 5 MΩ → tolerance ±12%
R_iso_corrected = 1. 5 MΩ – 1. 5 MΩ * .12 = 924 kΩ
4. .2 Measured value quality
For every insulation resistance value (R_iso_original / R_iso_corrected) there is a quality information (Quality)
which reflects the reliability of the measured insulation resistance value.
In a stable HV system without voltage fluctuations the quality is always between 9 % and 1 %.
When the HV voltage is instable, the currently performed measurement may be aborted. The obtained
measured values are characterised internally as invalid and are discarded by the statistical filtering. In the event
that such results occur too often over a short period of time, the statistical averaging is impaired, which is
signalled by the quality information.
4. . Partial resistances RF+ (R_iso_pos) and RF- (R_iso_neg)
The overall insulation resistance corresponds to the parallel connection of the two partial resistances of RF+
and RF-, in each case to earth.
The two partial resistances R_iso_pos (RF+) and R_iso_neg (RF-) are calculated from the overall insulation
resistance using the residual voltage (voltage difference URF+ and URF-). For this an HV voltage of at least 1 V
is needed, if not, the two partial resistances are output as SNV.
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ISOMETER® iso175
Wiring example
4. .4 Fast start measurement
The ISOMETER® includes a fast start measurement that is dependent on the selected profile. After a restart this
provides the user with a quick overview over the insulation status of the HV system before the first complete
measurement has been carried out. The following profiles support this function:
•1: Standard with fast startup (default)
•3: High Capactiy (capacitance) with fast startup
What is important here is that this function is only active during the device status R_iso_status = 0xFC
(estimated insulation value during startup). During this device status the user can also evaluate the status
information: Warnings_and_Alarms, bit 9 (Unsafe to Start). As soon as this signal displays the value false, the
insulation resistance of the connected system is at least twice the configured insulation parameter: Isolation
Threshold_Warning.
During this device status, interim values (“estimated“ values) of the insulation resistance with a period duration
of 2 ms are calculated. Characteristic for the behaviour of these interim values over time is that in a stable
HV system (no voltage fluctuation) the measured value increases steadily until the complete insulation
measured value is available. To facilitate evaluating the reliability of the calculated interim values (estimation),
every estimate is furnished with the corresponding quality information (Isolation: Quality). Both measured
values (Estimated, Quality) are already evaluated internally, and the result is output as the signal Status:
Warnings_and_Alarms, bit 9.
The evaluation of the two measured values is based on the following:
Condition1:
The currently calculated interim value (estimated value) must correspond to at least twice the alarm-warning
threshold (Isolation: Threshold_Warning).
Condition2:
The quality of the measured value must be at least 8 %.
When both conditions are met, the HV system is considered safe and the signal status: Warnings_and_Alarms,
bit 9 = false is set.
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Function
However, the interim values (estimated values) are only calculated when the following conditions have been
met by the HV system:
Condition1:
The voltage of the HV system must be stable for at least 2 ms within the first 3s after the insulation
measurement has been started, i. e. the voltage may not change by more than .4V / 2 ms (default value).
This threshold value can be changed by the user, if necessary (Isolation: Threshold_first_reference_estimation).
Condition2:
The difference of the two voltages HV_neg_to_Earth and HV_pos_to_Earth may not exceed a threshold value,
the Pre_estimation_max_difference. This threshold value can be changed correspondingly by the user, if
necessary.
As soon as both conditions are met, calculation of the interim (“estimated“) values is started. In the event that
these two conditions are not yet fulfilled after maximally 3s, the fast start measurement is aborted and interim
values (“Estimateds“) are no longer calculated. As long as the device status is R_iso_status = 0xFC, the signal
Status: Warnings_and_Alarms, bit 9 no longer changes its value (true). In this case users need to wait for the
first measured value (Device status R_iso_status = 0xFE) so that they can evaluate the insulation status of the HV
system.
The signal Isolation: Measurement_Counter can be used to determine whether a fast start measurement
is still active or whether it has been aborted. As long as the measured value counter is incremented with a
frequency of 5Hz, the fast start measurement is active.
4.4 Self test
4.4.1 Online self test
The online self test includes all device-internal test functions that are performed automatically and periodically
in the background and do not influence an active insulation resistance measurement. If one or more test
functions fail, a device error is triggered (Device Status: Device_Error, bit ).
When such an error occurs, the technical support (see chapter “Service and Support”, page 5) shall be
contacted.
In addition to the device-internal test functions, the electrical connection of connector LV pin 3 (E) to
chassis ground is checked. The result of this test can be evaluated by reading out the signal Status:
Warnings_and_Alarms, bit 3. In contrast to the online test functions described above, a fault of the chassis-
ground connection does not result in a device error.
ADVICE
For the function which tests the chassis-ground connection to work properly, the LV pin 1 connector
must also be connected to the chassis ground potential. We recommend making this connection not
directly at the device but via the chassis-ground potential. This ensures that the entire connection
line from LV-pin 3 to chassis ground is monitored.
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ISOMETER® iso175
4.4.2 Offline self test
The offline self test checks the following device functions:
•Electrical connection from connector HV+ to connection cable HV_pos (L+)
•Electrical connection from connector HV- to connection cable HV_neg (L-)
ADVICE
During the test only the electrical connection is checked, the polarity of the connection, however, is
not checked.
This offline self test can be carried out at any time during the operating mode “normal insulation
measurement“ (R_iso_status = 0xFE) by sending the control command Self test: Trigger_self_test with the
content (Data1) = 1. Here care must be taken that the offline self test is carried out only when the connection
switch to chassis ground (earth disconnector) is closed (Signal Earthlift: Status = 0x00). The self test takes ≤ 1s.
In case the connection switch first needs to be closed, an additional delay time of maximal 1s must be taken
into account.
Reading out the signal Status: Device_Activity permits verifying whether the offline self test is still ongoing
or whether it was fully completed. As long as the test is ongoing, this command is answered with
the value (Data1) = 2. The results of the offline self test are obtained by reading out the signal Status:
Warnings_and_Alarms, bits 1 and 2).
Bit 1: true = HV_pos connection failure
Bit 2: true = HV_neg connection failure
Please note that when there is a faulty earth connection, also the two connection tests to HV_pos and HV_neg
will signal an error, because for these tests a connection to chassis ground is indispensable.
4.4. Offline and communication self test
This test function can be started any time during the operating mode “normal insulation
measurement“ (R_iso_status = 0xFE) by sending the control command Self test: Trigger_self_test with the
content (Data1) = 2. In addition to the described offline self test, this function also performs a test of the status
output OKHS (LV pin 8). For this, the status output is switched to low for approx. 5 s during the self test. During
this time, the alarm ‘Status: Warnings_and_Alarms, Bit ’ is also active (true).
4.4.4 Periodical / automatic self test
The ISOMETER® offers users the possibility of carrying out an automated offline self test at periodic intervals. By
programming the parameters Self test: Period, they can set the period duration as needed in 1 s increments.
Please note that the first test is only started when the device is in the operating mode “normal insulation
measurement“ (R_iso_status = 0xFE) and the configured time interval has passed.
ADVICE
The first automated self test is performed 1 h after switching on the supply voltage. Should the
continuous operating time of the unit be < 1 h, it is recommended to adjust the period accordingly,
so that the connection check is carried out appropriate. In the event that the periodical self test is
deactivated (period duration = ), the user is responsible for the appropriate connection to the HV
system.
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Function
4.5 Measurement profiles
The ISOMETER® offers users different measurement profiles which they can use to better adapt their device to
the respective HV system. This adaptation can be performed in 2 ways:
Temporarily: If sudden disturbances occur in an HV system, e.g. significant HV voltage fluctuations, users
can change the active profile in the operating mode “normal insulation measurement“ at any time (Isolation:
ActiveProfile). This change will remain active until the device is restarted. After a restart the “Power-On“ profile
(Isolation: Power-On_Profile) is set as the active profile.
Permanently: The device offers users the possibility of changing the measurement profile to be used
permanently so that it remains active even after a restart of the device. To this end the parameters Isolation:
Power-On_Profile must be changed to the desired measurement profile.
4.5.1 Available measurement profiles
Standard
•Suitable for system leakage capacitances ≤5µF
•Internal digital 1Hz filter
•Internal statistical filtering of several individual measured values
•Maximum measuring time for one individual measurement ≤3 s
Standard with fast startup
•Same as the properties of the ‘Standard’ profile + fast start measurement active
High Capacity (capacitance)
•Suitable for system leakage capacitances ≤1 µF
•Internal digital 1Hz filter
•Internal statistical filtering of several individual measured values
•Maximum measuring time for one individual measurement ≤6 s
High Capacity (capacitance) with fast startup
•Same as the properties of the High Capacity profile + fast start measurement active
Disturbed
•Suitable for HV systems with voltage changes <1 Hz
•Internal digital .1Hz filter
•Internal statistical filtering of several individual measured values
•Maximum measuring time for one individual measurement ≤6 s
Service
•Suitable for a fast insulation measurement without internal statistical filtering (service function, not suitable
or recommended for the operating mode ‘normal insulation measurement’)
•Suitable for system leakage capacitances ≤1 µF
•Internal digital 1Hz filter
•Maximum measuring time for one individual measurement ≤6 s
Custom profile
•Reserved: This profile is reserved for customer-specific adaptations to a specific HV system, for which the
available standard profiles do not supply the measurement results desired in terms of measured value
tolerance. For further information, see customer configuration under ‘“Ordering information”, page 33’.
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ISOMETER® iso175
4.6 Chassis-ground connection
The device can use a CAN command (Earthlift: Status) to separate the chassis-ground connection.
The chassis-ground connection must always be disconnected when a further isometer monitors the HV
system. If the chassis-ground connection were not separated, a further isometer would measure also the
internal resistance of the ISOMETER® and hence output a false value for the insulation resistance of the HV
system (parallel connection of the ISOMETER® internal resistance and the insulation resistance of the HV
system). Also, connected isometers can disturb each other (voltage of the measuring pulse). The result of such
a disturbance may be considerable deviations in the measured values.
4.7 Unbalance measurement
To evaluate the distribution (symmetrical or asymmetrical) of the overall insulation resistance of an HV system,
users can analyse the following measured value: Unbalance: Measured_Value. This measured value indicates
the percentage distribution of the overall insulation value.
When the measured value is <5 %, the lower insulation resistance is on HV_pos to chassis ground, with a
measured value that is >5 %, it is correspondingly on Hv_neg to chassis ground.
As soon as a new measured value is available, the corresponding measured value counter is incremented
accordingly (Unbalance: Measurement_Counter). When the measured value exceeds or is below a threshold
that can be configured by the user (Unbalance: Threshold) an alarm can be triggered in addition (Status:
Warnings_and_Alarms).
When the threshold + 5 % hysteresis exceeds, the alarm bit is automatically deleted again (Condition: Self-
holding Alarm: Activation = 0xFC).
For this the following conditions must be met:
•HV voltage ≥ 2 V
•R_iso_status = ‘Normal Measure’ ( xFE)
•Earth disconnector closed
Examples
Example 1:
Unbalance Threshold = 4 [%]
HV voltage = 1 V
R_iso_neg = 1MΩ
R_iso_neg = 1MΩ
In this case the measured value ‘Unbalance’ is 5 [%].
Example 2:
Unbalance Threshold = 4 [%]
HV voltage = 1 V
R_iso_neg = 78 kΩ
R_iso_pos = 122 kΩ
In this case the measured value “Unbalance“ is 61[%].
Evaluation of the unbalance-alarm status: 1 % - 61% = 39% → the value is below the threshold value
“Unbalance Threshold“ and an “Unbalance Alarm“ is triggered.
Example3:
Unbalance Threshold = 4 [%]
HV voltage = 1 V
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Function
R_iso_neg = 122 kΩ
R_iso_pos = 78 kΩ
In this case the measured value “Unbalance“ is 39[%].
Evaluation of the unbalance-alarm status: 39% →the value falls hence short of the threshold value “Unbalance
Threshold“ and an “Unbalance Alarm“ is triggered.
The hysteresis for resetting the alarm status is 5%, i.e. when the measured value is ≥ unbalance threshold +
5%, the alarm is reset.
4.8 Measuring the system leakage capacitance
The ISOMETER® is furnished with a measuring function that serves to determine the overall system leakage
capacitance of the HV system (‘Capacity’: Measured_value). Among other things this measured value serves to
select a suitable measurement profile for the insulation measurement (Standard / High Capacity).
As soon as a new measured value is available, the corresponding measured value counter is incremented
accordingly (Capacity: Measurement_Counter).
4.9 Voltage measurement
The following voltages are measured
•HV-system voltage (Voltage: HV_System)
•HV_pos to chassis_ground (Voltage: HV_pos_to_Earth)
•HV_neg to chassis_ground (Voltage: HV_neg_to_Earth)
Depending on the specific configuration, the voltage measured values can contain the following voltage
components:
•AC + DC (Voltage: Mode = 0xFC)
•AC (Voltage: Mode = 0xFD)
•DC (Voltage: Mode = 0xFE)
The described measured values are always updated together, and the corresponding measured value counter
is incremented accordingly (Voltage: Measurement_Counter).
In addition, the ISOMETER® is furnished with a configurable undervoltage detection (Voltage:
Threshold_Undervoltage), which triggers a corresponding alarm when the value falls below the programmed
threshold value (Status: Warnings_and_Alarms).
4.10 Monitoring functions
4.10.1 Device error
As a general rule, a device error alarm (Status: Warnings_and_Alarms, bit ) is only active as long as the
condition for signalling the alarm is met.
4.10.2 HV system
The ISOMETER® provides users with various monitoring functions regarding the condition of the HV system so
that they can respond immediately to possible critical situations.
The device also offers the possibility of retaining an alarm event until a user resets it manually. In this manner
users can record also very brief alarm events and evaluate them at a later time.
To this end the parameters Self-holding Alarm: Activation= 0xFD must be set. By sending the command Self-
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ISOMETER® iso175
holding Iso-Alarm = 0x0 users can reset all active alarm bits, provided that the corresponding alarm condition
is no longer met.
HV+ to chassis-ground error
The ISOMETER® offers the possibility of checking the electrical connection between HV+ and chassis ground.
For this purpose the offline self test must be carried out (see chapter “Offline self test”, page 15). A faulty
connection is indicated with the signal Status: Warnings_and_Alarms, bit .
ADVICE
Prerequisite for proper functioning of this check is a system leakage capacitance ≥1 nF between
HV+ and chassis ground.
HV- to chassis-ground error
The ISOMETER® offers the possibility of checking the electrical connection between HV- and chassis ground.
For this purpose the offline self test must be carried out (see chapter “Offline self test”, page 15). A faulty
connection is indicated with the signal Status: Warnings_and_Alarms, bit 2.
ADVICE
Prerequisite for proper functioning of this check is a system leakage capacitance ≥1 nF between
HV- and chassis ground.
Chassis-ground connection faults
The ISOMETER® continuously monitors the connection between LV pin 3 (earth connection) and chassis
ground (see chapter “Online self test”, page 14). A faulty connection is indicated with the signal Status:
Warnings_and_Alarms, bit 3.
ADVICE
Prerequisite for proper functioning of this check is that the LV pin3 connection is on the same
potential as terminal31. Making this connection at chassis ground is recommended. This ensures
that LV pin 3 is connected not only to terminal31 but actually to chassis ground, which is the
precondition for a functioning insulation measurement. For a correct connection, the ohmic
resistance between LV pin 3 and chassis ground must be ≤2kΩ. With an ohmic resistance ≥ 4kΩ a
connection fault is definitely recognised, and the corresponding alarm bit is set.
Insulation resistance fault (alarm)
The ISOMETER® signals a fault of the insulation resistance (Status: Warnings_and_Alarms, bit 4), when the
measured value falls short of the threshold value Isolation: Threshold _Error. The alarm bit is reset provided that
the currently measured insulation resistance is ≥ (Isolation: Threshold _Error + 25% hysteresis).
ADVICE
The two parameters Isolation: Threshold_Error and Isolation: Threshold_Warning are cross-checked
for plausibility. When the parameter Isolation: Threshold_Error >Isolation: Threshold_Warning a
Device_Error_Alarm is triggered.
Insulation resistance warning (prewarning)
The ISOMETER® signals a fault of the insulation resistance (Status: Warnings_and_Alarms, bit 5), when the
measured value falls short of the threshold value Isolation: Threshold_Warning. The alarm bit is reset provided
that the currently measured insulation resistance is ≥ (Isolation: Threshold _Warning + 25% hysteresis).
iso175_D 415_ 1_M_XXEN/11.2 23 19

Function
Insulation resistance measured value no longer up to date
The ISOMETER® offers the possibility of monitoring automatically whether the insulation resistance measured
value is updated within a defined time period (parameter Isolation: Threshold_Timeout_Measurement). If the
measured value has not been updated within the defined time period, the corresponding alarm bit (Status:
Warnings_and_Alarms, bit 6) is set. As soon as the insulation resistance measured value has been updated, a
possibly active alarm is reset automatically (prerequisite: Self-holding Alarm: Activation = 0xFC).
ADVICE
For proper functioning of this feature, the maximum measuring time for an individual measurement
(dependent on the respective profile) must be selected for the Threshold_Timeout_Measurement ≤,
since after the maximum measuring time has expired an ongoing measurement is aborted and a new
measurement is automatically started (see chapter “Measurement profiles”, page 16).
HV voltage unbalance faults
When the function (Unbalance: Threshold > 0) is activated, the ISOMETER® monitors the two partial voltages
HV+ and HV-, in each case against chassis ground. Prerequisite for this is that the HV voltage is ≥2 V (Voltage:
HV_System). As soon as the percentage share of the smaller voltage component falls below the programmed
threshold value, the corresponding alarm bit (Status: Warnings_and_Alarms, bit 7) is set. When the threshold
value + 5% hysteresis is exceeded again, the set alarm bit is deleted automatically (prerequisite: Self-holding
Alarm: Activation = 0xFC).
Undervoltage error
When the function (Unbalance: Threshold_Undervoltage > 0) is activated, the ISOMETER® monitors the HV-
system voltage (Voltage: HV_System). If the HV-system voltage falls below the configured threshold value, the
corresponding alarm bit (Status: Warnings_and_Alarms, bit 8) is set. When the threshold value + 5% hysteresis
is exceeded again, the set alarm bit is deleted automatically (prerequisite: Self-holding Alarm: Activation = 0xFC).
System condition unstable (fast start measurement)
An active alarm bit (Status: Warnings_and_Alarms, bit 9) signals an unstable HV-system condition with respect
to the insulation resistance (see chapter ‘“Fast start measurement”, page 13’).
Earth disconnector open
The device signals an alarm (Status: Warnings_and_Alarms, bit 0) as soon as the disconnector for the chassis-
ground connection is open, as no insulation measurement can be carried out with this condition. As soon
as the disconnector has been closed again, the corresponding alarm bit is deleted (prerequisite: Self-holding
Alarm: Activation = 0xFC ).
4.10. Status output OKHS
The status output is designed as an open collector topology and connects to terminal 15, when no alarm is
active (Status: Warnings_and_Alarms = ). As soon as at least one alarm is active, the internal output transistor
locks so that the external pull-down resistor pulls the output to the terminal 31 potential.
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