EN1434-2_2006D
Document type: European Standard Document subtype:
Document stage: CEN Enquiry Document language: E
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CEN/TC 176
Date: 2006-03
prEN 1434-2:2006
CEN/TC 176 Secretariat: DS
Heat Meters — Part 2: Constructional requirements
W?rmez?hler — Teil 2: Anforderungen an die Konstruction
Compteurs d'énergie thermique — Partie 2 : Prescriptions de fabrication ICS: Descriptors:
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Contents Page
Foreword..............................................................................................................................................................4 1 Scope......................................................................................................................................................4 2 Normative references............................................................................................................................4 3 Temperature sensors............................................................................................................................5 3.1 General....................................................................................................................................................5 3.2 Mechanical design.................................................................................................................................5 3.2.1 Materials of temperature probe sheath and pocket...........................................................................5 3.2.2 Dimensions of direct mounted short probes - Type DS....................................................................6 3.2.3 Dimensions of direct mounted long probes - Type DL......................................................................6 3.2.4 Dimensions of pocket mounted long probes - Type PL....................................................................8 3.2.5 Dimensions of temperature pocket......................................................................................................8 3.2.6 Design of short probes with respect to installation.........................................................................10 3.2.7 Design of long probes with respect to installation..........................................................................10 3.3 Platinum temperature sensor.............................................................................................................10 3.3.1 Specialised definitions for 2 wire temperature probes....................................................................10 3.3.2 Resistance characteristics .................................................................................................................11 3.3.3 Signal leads..........................................................................................................................................12 3.3.4 Temperature sensors for the 2-wire method ....................................................................................12 3.3.5 Temperature sensors for the 4-wire method ....................................................................................13 3.3.6 Thermal response time .......................................................................................................................13 3.4 Other temperature sensors.................................................................................................................13 4 Flow sensors........................................................................................................................................13 4.1 Maximum admissible working pressure, PS in bar..........................................................................13 4.2 Sizes and dimensions.........................................................................................................................13 4.3 Test signal output................................................................................................................................15 4.4 Adjusting device..................................................................................................................................15 5 Calculators ...........................................................................................................................................15 5.1 Mechanical dimensions for calculators for domestic use...............................................................15 5.2 Terminals - specification and identification......................................................................................16 5.2.1 Terminals for signal leads ..................................................................................................................16 5.2.2 Terminals for connection to the mains supply.................................................................................17 5.3 Batteries................................................................................................................................................18 5.4 Dynamic behaviour..............................................................................................................................18 5.5 Test signal output................................................................................................................................18 5.6 24 hours interruption in supply voltage............................................................................................18 6 Complete meter....................................................................................................................................18 7 Interfaces between sub-assemblies..................................................................................................18 7.1 Definitions for pulse device interfaces..............................................................................................19 7.1.1 Electrical connection...........................................................................................................................19 7.1.2 Classification of pulse output devices..............................................................................................19 7.1.3 Timing and electrical parameters for pulse output devices (other than test signals)..................20 7.1.4 Classification of pulse input devices ................................................................................................20 7.1.5 Timing and electrical parameter for pulse input devices................................................................21 7.1.6 Compatibility........................................................................................................................................21 8 Marking and security seals.................................................................................................................22 8.1 Marking.................................................................................................................................................22 8.1.1 Temperature sensor pairs...................................................................................................................22 8.1.2
Pockets (22)
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8.1.3 Flow sensor..........................................................................................................................................22 8.1.4 Calculator.............................................................................................................................................23 8.1.5 Complete meter ...................................................................................................................................23 8.2 Sites for marking.................................................................................................................................24 8.3
Security seals (24)
Annex A (informative) Examples of temperature sensors............................................................................25 Annex B (normative) Input and output test signals......................................................................................34 Annex C (informative) Low voltage Power Supply for heat meters and their sub-assemblies ................37 C.1 Remote supply.....................................................................................................................................37 C.1.1 Voltage (DC or AC)..............................................................................................................................37 C.1.2 Current available .................................................................................................................................37 C.1.3 Cabling requirements..........................................................................................................................37 C.2 Local external DC supply....................................................................................................................37 C.2.1 Voltage..................................................................................................................................................37 C.2.2 Other data.............................................................................................................................................38 C.3 Power supply specifications.. (38)
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Foreword
This document (prEN 1434-2:2006) has been prepared by Technical Committee CEN/TC 176 “Heat Meters”, the secretariat of which is held by DS.
This document is currently submitted to the CEN Enquiry. The other parts are
Part 1 - General requirements Part 3 - Data exchange and interfaces Part 4 - Pattern approval tests Part 5 - Initial verification tests
Part 6 - Heat meter installation, commissioning, operational monitoring and maintenance
1 Scope
This European Standard applies to heat meters, that is to instruments intended for measuring the heat which, in a heat-exchange circuit, is absorbed or given up by a liquid called the heat-conveying liquid. The heat meter indicates the quantity of heat in legal units.
Electrical safety requirements are not covered by this standard. Pressure safety requirements are not covered by this standard.
Surface mounted temperature sensors are not covered by this standard.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. EN 1434-1 Heat meters - Part 1: General requirements EN 1434-3 Heat meters - Part 3: Data exchange and interfaces EN 60751:1995
Industrial platinum resistance thermometer sensors
EN 60947-5-6:2000 (E) X
Low-voltage switchgear and controlgear. Part 5-6: Control circuit devices and switching elements - DC interface for proximity sensors and switching amplifiers (NAMUR)
ISO 228-1
Pipe threads where pressure tight joints are not made on the threads - Part 1: Dimensions, tolerances, and designation
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ISO 4903 Information technology - Data communication - 15 - pole DTE/DCE interface connector and contact number assignments ISO 7005-1 Metallic flanges. Part 1: Steel flanges ISO 7005-2 Metallic flanges. Part 2: Cast iron flanges.
ISO 7005-3
Metallic flanges. Part 3: Copper alloy and composite flanges
3 Temperature sensors
3.1 General
The temperature sensor sub-assembly shall consist of platinum resistance temperature sensors selected as matched pairs.
Other types of temperature sensor pairs may be used, where the sub-assembly consists, inseparably, of temperature sensors and calculator.
The maximum admissible working pressure shall be declared by the supplier. Where no dimensional tolerance is specified, the values shall be taken from table 1.
Table 1 — Tolerances
Dimension mm
0,5 up to 3
over 3 up to 6 over 6 up to 30 over 30 up to 120 over 120 up to 400
Tolerance mm
±0,2
±0,3
±1
±1,5
±2,5
3.2 Mechanical design
For pipe sizes up to and including DN 250, 3 different temperature sensor types are standardised: Direct mounted short probes - Type DS Direct mounted long probes - Type DL Pocket mounted long probes - Type PL
Types PL and DL can be either head probes or have permanently connected signal leads. Type DS shall have permanently connected signal leads only.
3.2.1 Materials of temperature probe sheath and pocket
The temperature pocket and the protective sheath of direct mounted probes shall be of a material, that is adequately strong and resistant to corrosion and has the requisite thermal conductivity. A suitable material has been shown to be EN 10088-3 - X6 Cr Ni Mo Ti 17 12 2
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3.2.2 Dimensions of direct mounted short probes - Type DS
The dimensions shall be as given in figure 1.
Further non-normative information is given in annex A, figure A.1
The qualifying immersion depth shall be 20 mm – or less if so specified by the supplier.
3.2.3 Dimensions of direct mounted long probes - Type DL
The dimensions shall be as given in figure 2.
Further information is given in annex A, figure A.2 and A.3
The qualifying immersion depth shall 50 % of the length B – or less if so specified by the supplier.
All dimensions in mm
Figure 1 — Temperature probes type DS
Legend:
1: Temperature sensing element
2: Protective sheath
3: Sealing ring
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All dimensions in mm
Figure 2 — Temperature probes type DL (Head or cable)
Legend:
G 1/2 B thread in accordance with ISO 228-1
A: < 30 mm or ≤ 50 mm for PT1000
Alternative lengths
B C Head probe only
85 105
120 140
210 230
1: Temperature sensing element
2: Protective sheath
3: Sealing face
4: Outline of head probe
5: Outline of permanently connected signal lead probe
6: Inlet for signal cable – ? ≤ 9 mm
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3.2.4 Dimensions of pocket mounted long probes - Type PL
The dimensions shall be as given in figure 3.
Further information is given in annex A, figure A.4 and A.5
The qualifying immersion depth shall 50 % of the length B for the shortest pocket specified – or less if so specified by the supplier.
3.2.5 Dimensions of temperature pocket
The temperature pocket is designed for use with type PL temperature probes only. It is designed to be capable of being inserted through a pipe wall to which has been externally brazed or welded a boss (see annex A, figure A.6 a and b.) and in this respect only, it is interchangeable with a direct mounted long probe of corresponding insertion length. The dimensions shall be as given in figure 4. The dimensions shall be as given in figure 4.
All dimensions in mm
Figure 3 — temperature probes – Type PL (Head or cable)
Legend:
1)
Corresponding to c11 in ISO 286-2, rounded to 2 decimals.
A: < 30 mm or ≤ 50 mm for PT1000
Alternative lengths B (Head probe only)
105
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140
230
1: Temperature sensing element
2: Outline of head probe
3: Outline of permanently connected signal lead probe
4: Inlet for signal cable – ? ≤ 9 mm
All dimensions in mm
Figure 4 — Temperature pocket
Legend:
1) Corresponding to H11 in ISO 286-2 rounded to 2 decimals.
G 1/2 B thread in accordance with ISO 228-1
Alternative lengths
C D
85 ≤ 100
120 ≤ 135
210 ≤ 225
1: Sealing face
2: Probe clamping screw with provision for security sealing
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3.2.6 Design of short probes with respect to installation
The sensor shall be mounted perpendicular to the flow and with the sensing element inserted to at least the centre of the pipe.
For internal pressures up to 16 bar, the sensor shall be designed to fit in a pipe fitting (see annex A, figure A.7).
3.2.7 Design of long probes with respect to installation
The sensor shall be mounted with the sensing element inserted to at least the centre of the pipe.
The sensor shall be designed to fit in the following types of installation, (for internal pressures up to PN16):
a) in a pipe DN 50 mounted with the tip pointing into the flow in a bend (see annex A, figure A.8B), using welded-in boss (see annex A, figure A.6 b).
b)
in a pipe DN 50 mounted at an angle 45o to the direction of the flow with the tip pointing into the flow (see annex A, figure A.8 c), using a welded in boss (see annex A, figure A.6 b).
c)
in a pipe DN 65 to DN 250, mounted perpendicular to the flow (see annex A, figure A.8 d), using a welded-in boss (see annex A, figure A.6 a).
3.3 Platinum temperature sensor
3.3.1
Specialised definitions for 2 wire temperature probes
Figure 5 — Temperature probe with permanently connected signal leads
Legend:
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R 1: Temperature sensing element resistance 1: Temperature sensing element R 2: Internal wire resistance 2: Protective sheath R 3: Signal lead resistance 3: Mounting thread 4: Signal leads
Figure 6 — Head sensor temperature probe
Legend:
R 1: Temperature sensing element resistance 1: Temperature sensing element R 2: Internal wire and terminals resistance 2: Protective sheath 3: Mounting thread 4: Outline of head
3.3.2 Resistance characteristics
The calibration of temperature sensors shall be traceable to national temperature standards. The intermediate values of the heat meter temperature sensor shall be interpolated using the EN 60751 formula as follows: R 1 = R 0 (1 + At + Bt 2
)
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where: R 1 is the resistance value at temperature t in ? (excluding cable resistance - see figures 5 and 6) R 0 is the resistance value at temperature 0 oC in ? (base value) (excluding cable resistance) A is 3,9083 × 10-3
oC -1
B
is - 5,775 × 10-7
oC -2
NOTE It is assumed, that the national temperature standards are established with reference to ITS-90 - The International Temperature Scale of 1990.
3.3.3 Signal leads
For signal leads, leads with strands can be used, or in the case of head probes, solid wires. The lead ends shall be precisely trimmed, if strands are used (e.g. by lead end sleeves). Solder-coating of the lead ends to prevent splicing is not permissible.
A soldered joint to connect the temperature probe signal lead to the calculator is only permitted in the case of non-interchangeable temperature probes.
For screened cables for temperature sensors there shall be no connection between the screen and the protecting sheet.
3.3.4 Temperature sensors for the 2-wire method
The length and cross sectional area of signal leads of paired resistance sensors of separable sub-assemblies shall be equal.
The length of the signal lead as supplied by the manufacturer shall not be changed. The length shall be within the values given in table 2.
Table 2 — Maximum lengths of leads for Pt 100 temperature sensors
Lead cross section
mm 2
Max. length for Pt 100 m
0,22 0,50 0,75 1,50
2,5 5,0 7,5 15,0
For sensors of higher resistances the limiting value can be extended proportionally.
NOTE
The values given in Table 2 have been obtained in the following manner:
It is assumed, that the difference in temperature of the leads does not exceed one third of the temperature difference between flow and return pipes. The maximum permissible length of lead for each lead cross section was then calculated, having decided that the error created may not be allowed to exceed 0,2 times the maximum permissible error of the temperature probe pair and using the knowledge of the different resistances created by the temperature differences between the flow and return leads.
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The influence of the length of a signal lead can be neglected, if the total resistance of a lead for a Pt 100 temperature sensor does not exceed two times 0,2 .
3.3.5 Temperature sensors for the 4-wire method
If the cable length requirements in 2.3.4 cannot be fulfilled, the 4-wire method shall be used. The connections shall be clearly identifiable so that they cannot be confused.
A cross-section of 0,5 mm 2
is recommended for head sensors and a minimum cross-section of 0,14 mm 2
for cable sensors.
3.3.6 Thermal response time
The supplier shall declare the temperature sensor response time τ0,5 as defined in 4.3.3 of EN 60751:1995, using the test method in 4.3.3.3 of EN 60751:1995.
3.4 Other temperature sensors
Other types of temperature sensors are permissible, but shall be tested as part of the calculator.
4 Flow sensors
4.1 Maximum admissible working pressure, PS in bar
The maximum admissible working pressure shall be declared by the manufacturer.
4.2 Sizes and dimensions
The flow sensor is designated either by the thread size of the end connections or by the nominal diameter of the flange. For each flow sensor size there is a corresponding value of the permanent flow rate q p and a set of lengths as given in tables 3 and 4.
The values in table 3 apply to the connecting screw and/or the flange, and the overall lengths. For sizes larger than DN 250 the flow sensor dimensions are not standardised.
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Table 3 — Dimensions
Preferred Also acceptable Also acceptable
q p m3/h Overall
length
mm
Threaded
end con-
nections
Flanged
connec-
tions
DN
Overall
length
mm
Threaded
end con-
nections
Flanged
connec-
tions
DN
Overall
length
mm
Threaded
end con-
nections
0,6 1,0 1,5 2,5 3,5 6,0 10 15 25 40 60 100 150 250 400 110
130
165
190
260
260
300
300
300
350
350
350
500
500
600
G 3/4 B
G 3/4 B
G 3/4 B
G 1 B
G 1 1/4 B
G 1 1/2 B
G 2 B
15
15
15
20
25
32
40
50
65
80
100
125
150
200
250
190
190
190
260
270
300
360
G 1 B
G 1 B
G 1 B
G 1 1/4 B
20
20
20
25
50
80
100
110
110
130
G 3/4 B
G 3/4 B
G 1 B
To achieve the necessary overall length adaptor pieces can be fitted.
The adjacent lengths larger or smaller than the preferred lengths may be adopted for q p 10 m3/h
Tolerances on the overall length shall be:
Up to 300 mm 02?mm
From 350 to 600 mm 03? mm
Threaded connection.
Dimensions for the threaded end connections are specified in table 4. Threads shall comply with ISO 228-1. Figure 7 outlines the dimensions a and b.
Flanged connection
Flanged end connections shall comply with ISO 7005-1, 7005-2 and 7005-3 (as appropriate) for a nominal pressure corresponding to that of the flow sensor.
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Table 4 — Threaded end connections Range of size and minimum thread lengths in mm
Thread a
b
G 3/4 B G 1 B G 1 1/4 B G 1 1/2 B G 2 B
10 12 12 13 13
12 14 16 18 20
Figure 7 — Outline of the dimensions a and b in Table 4
4.3 Test signal output
For test purposes, it is required that either high resolution pulses using an adaptor according to annex B shall be provided, or data from a serial interface, as described in EN 1434-3, using an adapter (if necessary) shall be employed . The discrimination of these test outputs shall be such, that in a test at q i (defined in 5.3 of EN 1434-1:2006), the measurement error resulting from the number of pulses is not greater than 0,8%, and the test period of 1h for sizes q p . ≤ 10 m 3/h or 1,5 h for q p ≥ 10 m 3/h, is not exceeded.
The nominal relationship between the signal emitted and the quantity measured shall be declared by the supplier.
Output names used at pulse output connections are given in annex B.
4.4 Adjusting device
The flow sensor may be fitted with an adjustment device making it possible to correct the relationship between the indicated and the true value.
5 Calculators
5.1 Mechanical dimensions for calculators for domestic use
The casing of calculators intended for wall mounting shall have maximum dimensions given in figure 8.
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If the casing is large enough, the centre distances for the mounting holes shall be as in figure 8. If the casing
is smaller, an adapter plate shall be available.
Figure 8 — Maximum dimensions in mm
5.2 Terminals - specification and identification
The numbers specified shall be used for the inscriptions on the terminals provided. Terminals not required can be omitted. The screening of a screened cable may be connected to the terminal board for earthing purposes. The screening of a screened cable may be anchored to the terminal board to prevent damage of the cable by pulling, provided the cable used is suitable for this. 5.2.1 Terminals for signal leads
The terminals shall meet the following requirements:
a) Maximum cable cross-section 1,5 mm 2
. b) Distance between terminals 5 mm. c) Suitable for stranded wire.
d) The contact resistance for a two-wire Pt 100 transition between the terminal and the wire shall be ≤5 m ?. The change in contact resistance with time shall be < 5 m ?.
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Table 5 — Numbering of terminals
Terminal no. Signal descriptor
Signal iden-tification 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
High temperature sensor/assigned to No. 5* High temperature sensor/assigned to No. 6 * Low temperature sensor/assigned to No. 7 * Low temperature sensor/assigned to No. 8 * High temperature sensor High temperature sensor Low temperature sensor Low temperature sensor
Flow sensor, positive supply voltage output Flow sensor signal input Flow sensor reference input Test signals reference output
High resolution energy test signal output Flow pulse test signal input
High resolution volume test signal input Remote counting pulses energy output
Remote counting pulses energy output, reference level Remote counting pulses volume output
Remote counting pulses volume output, reference level CL 0 - interface with 4-wire CL 0 - interface with 4-wire CL 0 - interface with 4-wire CL 0 - interface with 4-wire Meter bus interface Meter bus interface -U CH CI CT CE CV
RX+/RTX+ RX-/RTX- TX+ TX-
* Used only with 4-wire method
Rules about numbering of terminals:
a) There may be more than one terminal, each of them having the same number, if they are electrically connected (e.g. connection of temperature sensor cable's shield).
b)
Terminals and their numbers can be omitted, if corresponding signals are not present.
c)
For signals other than those described, terminal number 50 and upwards shall be used.
5.2.2 Terminals for connection to the mains supply
Two or, preferably, three terminals shall be provided, which shall be suitable for stranded wire up to a cross-section of 2,5 mm 2
. Cables with permanently fitted connections may also be used.
Table 6 — Numbering and marking of the mains terminals
Terminal No
Marking 26 27 28
earth symbol N L
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If no polarity indication is needed, the "N" and "L" can be replaced by the standardized symbol for a mains connection.
5.3 Batteries
If a heat meter has interchangeable batteries, they shall be replaceable without damaging verification markings. The life time of the batteries shall be declared by the supplier.
5.4 Dynamic behaviour
The supplier shall declare, how the temperature measurements and integration are related to the flow sensor signal and time.
5.5 Test signal output
A high resolution energy signal is required for testing purposes. The resolution shall be sufficiently high so that at a test at the lower limit of temperature difference and/or flow rate, the additional error caused by the resolution of the energy signal can be shown to be insignificant. The nominal relationship between the high resolution signal and the energy reading shall be stated by the supplier.
The energy signal as specified above shall be available either directly at the calculator connection terminal or at the terminal of a testing adapter as stated in annex B.
The test signal shall be either pulses with a defined value of pulses/energy increment or a data output, specially defined, or a display with correspondingly high resolution. Pulse output names used at output connections are given in annex B.
5.6 24 hours interruption in supply voltage
The calculator shall be able to handle interruptions in the supply voltage for periods of up to 24 hours, without a change more than one digit in the energy display.
6 Complete meter
The requirements given in clauses 3 to 5 shall be applied where relevant.
A test output shall be provided, in which the resolution is high enough to ensure, that the reading error does not exceed 0,5 % for a test duration of 2 h.
The attachment of devices for sampling the test output shall have no effect on the accuracy of the heat meter. In addition the indicating device may be provided with a high resolution scale for testing purposes, provided that the resolution requirements are met.
It is assumed, that the reading error will not exceed half the smallest scale interval for each meter reading or, in the case of digital indicators, cannot exceed 0,99 of the least significant digit. Pulse output names used at output connections are given in annex B
7 Interfaces between sub-assemblies
The type of signals between the calculator, the temperature sensors and the flow sensor shall be clearly defined by the supplier.
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The definition shall include all relevant data, e.g. type of signal, voltage and current levels and limitations such as maximum and minimum frequency, duty cycles etc.
7.1 Definitions for pulse device interfaces
To define the compatibility between a unit with a pulse output and another unit with a pulse input, the following specification shall be used. 7.1.1 Electrical connection
The electrical connection of a pulse device has two terminals. Both terminals shall be isolated from ground (e.g. pipes or casing) with an insulation resistance greater than 100 M ? measured at 100 V DC under reference conditions.
The possible shielding connection shall be designed to the rules of the electromagnetic compatibility. 7.1.2 Classification of pulse output devices Class OA: electromechanical switch.
Typical examples of a class OA device is the Reed contact and the electronic switch. The ”ON” state is defined by the closed switch, the ”OFF” state by the open switch.
A characteristic feature of the electromechanical switch is bouncing of the mechanical contacts. Class OB: passive electronic current sink with slow pulses; high current.
Typical example for a passive electronic current sink class OB is the ”open collector” with a Darlington transistor. Class OB devices replace the typical models of class OA devices by an electronic solid state solution. These devices do not bounce and need an auxiliary power supply and electronic control signal to switch the current source ”ON” and ”OFF”.
Class OC: passive electronic current sink with slow pulses; low current.
Typical example for a passive electronic current sink class OC is also the ”open collector” or ”open drain” device. These devices do not bounce and need an auxiliary power supply and electronic control signal to switch the current source ”ON” and ”OFF”. This device has lower voltage drop than Class OB. Class OD: passive electronic current sink with fast pulses. low current Class OD devices differ from class OC devices by a shorter pulse length. Class OE: passive electronic current sink with fast pulses; higher current .
Current sink according EN 60947-5-6 (Namur). It differs from class OD by higher level of current and voltage. It allows to monitor the connecting cable on short and break.
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7.1.3 Timing and electrical parameters for pulse output devices (other than test signals)
Table 7 — Timing and electrical parameters
Parameter Class OA
Class OB
Class OC
Class OD
Class OE
Example Reed or electronic switch (Darlington) open collector
Open collector Open collector or active
Polarity reversal Possible
Not possible
Not possible
Not possible
Not possible Pulse length ≥ 100 ms ≥ 30 ms ≥ 100 ms ≥ 0,1 ms 0.04 ms Pulse pause ≥ 100 ms ≥ 100 ms
≥ 100 ms
≥ 0,1 ms
0.04 ms
Bounce time ≤ 1 ms
-- -- -- - Max. input voltage
30 V 30 V 6 V 6 V 12.5 V Max input current 27 mA 27 mA 0,1 mA 0,1 mA 17 mA ”ON” Condition
U ≤ 2,0 V at 27 mA
U ≤ 2,0 V at 27 mA U ≤ 0,3 V at 0,1 mA U ≤ 0,3 V at 0,1 mA I 2.2 mA
“OFF” Condition R 6 M ? R 6 M ?
R 6 M ?
R 6 M ?
I 1.0 mA
7.1.4 Classification of pulse input devices Class IA:
In a typical example, the actuating coil drives an electromechanical relay or an electromechanical counter - In combination with a fixed voltage source (specified DC voltage: 3 V, 12 V and 24 V), these devices work with class OA and OB pulse output devices. Class IB:
A typical example is a micro controller CMOS input with a low pass filter for protection against and suppression of bouncing parts of the pulse signal.
A pull-up resistor to stabilize the CMOS input is used as current source for class OC pulse output devices. Class IC:
Class IC devices are similar to Class IB devices, but the time constant of the low-pass filter is designed to be shorter. IC input devices cannot work with output devices that exhibit bouncing. Class ID:
Input device according EN 60947-5-6 (Namur). Similar to class IB with higher levels of current and voltage. The switching thresholds are defined as current levels.