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JJF 1835-2020
JJF
METERING TECHNICAL SPECIFICATION
OF THE PEOPLE’S REPUBLIC OF CHINA
Calibration specification for remote sensing
measurement systems of vehicle exhaust
ISSUED ON: JULY 02, 2020
IMPLEMENTED ON: JANUARY 02, 2021
Issued by: State Administration for Market Regulation
Table of Contents
Introduction ... 5 
1 Scope ... 6 
2 Reference documents ... 6 
3 Terms ... 6 
3.1 Remote sensing method ... 6 
3.2 Vehicle exhaust ... 6 
3.3 Opacity ... 6 
3.4 Standard reducing light dimmer ... 7 
3.5 Background value... 7 
4 Overview ... 7 
5 Metrological characteristics ... 7 
5.1 Exhaust gas measuring device ... 7 
5.2 Speed measuring device ... 8 
5.3 Road slope measuring device ... 8 
5.4 Meteorological parameter measuring device ... 9 
6 Calibration conditions ... 9 
6.1 Environmental conditions ... 9 
6.2 Calibration standards and other equipment ... 9 
7 Calibration items and calibration methods ... 11 
7.1 Gas measuring device ... 11 
7.2 Opacity measuring device ... 13 
7.3 Speed measuring device ... 14 
7.4 Road slope measuring device ... 17 
7.5 Meteorological parameter measuring device ... 17 
8 Representation of calibration result ... 19 
8.1 Calibration data processing ... 19 
8.2 Evaluation of uncertainty of calibration results ... 19 
8.3 Calibration certificate ... 20 
9 Recalibration time interval ... 20 
Appendix A Standard gas and its concentration requirements ... 21 
Appendix B Calibration record of remote sensing system for vehicle exhaust
... 22 
Appendix C Format of the inside page of the calibration certificate for the remote
sensing system of vehicle exhaust ... 25 
Appendix D Example of uncertainty evaluation of indication error calibration for
remote sensing system of vehicle exhaust ... 26 
Calibration specification for remote sensing
measurement systems of vehicle exhaust
1 Scope
This specification applies to the calibration of the remote sensing measurement
system for motor vehicle exhaust.
2 Reference documents
This specification refers to the following documents:
HJ 845 Measurement methods and technical requirements for exhaust
pollutants from diesel vehicles in use (remote sensing method)
JB/T 11996 General technical requirements of remote sensing equipment for
motor vehicle exhaust
For dated reference documents, only the dated version applies to this
specification; for undated reference documents, the latest version (including all
amendments) applies to this specification.
3 Terms
3.1 Remote sensing method
A method of remote sensing and measuring the exhaust gas concentration
of a driving motor vehicle using optical principles.
[Source: HJ 845-2017, 3.2, with modification]
3.2 Vehicle exhaust
The gaseous pollutants and particulate matter emitted from the exhaust pipe
of a motor vehicle, which refer to CO, CO2, HC, NO and particulate matter
in this specification.
3.3 Opacity
The flux absorption percentage of the light emitted from the light source
passes through the exhaust plume of the motor vehicle and reaches the light
receiver of the instrument, which is generally represented by the symbol N.
[Source: HJ 845-2017, 3.8, with modification]
3.4 Standard reducing light dimmer
A standard device that uses a physical method to block light from passing
through in accordance with a prescribed ratio, which is the opacity of the
standard reducing light dimmer.
3.5 Background value
The state of ambient gas before remote sensing of motor vehicle exhaust
gas, which refers to the environmental background value.
4 Overview
Remote sensing system for motor vehicle exhaust (hereinafter referred to as
remote sensing system) is a measurement system that uses remote sensing to
detect the exhaust of motor vehicles traveling within a specified speed range
under certain weather conditions and road slopes. It can measure the exhaust
gas value of motor vehicles on the road without affecting the normal driving of
motor vehicles. Its working principle is: the mainframe of the remote sensing
system emits a light beam; when a motor vehicle passes, the exhaust gas
interferes with the light beam; the spectrum, intensity and other characteristics
of the light received by the receiving end will change; this change can reflect
the concentration of the measured exhaust gas or changes in opacity. At
present, the light sources used in the remote sensing system are laser, infrared
heat radiation, ultraviolet light, yellow-green light.
The remote sensing system is mainly composed of exhaust gas measurement
devices (generally including gas measurement devices and opacity
measurement devices for measuring particulate pollutants, or only one of them),
speed measurement devices, road slope measurement devices,
meteorological parameter measurement devices, vehicle number plates
identification system, control and management computer system, etc. Its usage
is divided into the following three types: horizontal mobile remote sensing
system, horizontal fixed remote sensing system, vertical fixed remote sensing
system.
5 Metrological characteristics
5.1 Exhaust gas measuring device
5.1.1 Gas measuring device
- The arithmetic average of n measurements.
Where:
sa - Relative standard deviation.
7.1.3 Dynamic calibration of indication error of gas measuring device
7.1.3.1 Turn on the power supply and perform warm-up according to the time
specified in the gas measurement device manual. After the warmup is
completed, adjust the light path of the gas measurement device, to make the
gas measurement device meet the working requirements specified in the
manufacturer's manual.
7.1.3.2 After all preparations for the gas measuring device are completed and
the light path of the emission pollutant gas measuring device is not affected,
the gas calibration auxiliary device is placed in the detection light path to make
it meet the working requirements specified in the manufacturer's instructions.
The connection of the gas calibration auxiliary device is as shown in Figure 1.
7.1.3.3 When ready, read the background value of the gas measuring device.
Select the standard gas No.2 and No.3 as specified in Table A.1 or Table A.2. If
the standard gas in Table A.2 is used for testing, the corresponding standard
gas in Table A.1 must also be selected. Adjust the flow rate of the dynamic gas
calibration device to 20 L/min according to the requirements; the injection time
is about 0.5 s. Inject the standard gas into the dynamic gas calibration device
according to the predetermined procedure. Record the gas mole fraction
indication of the gas measuring device. Follow the above steps, to repeat the
measurement 3 times for each mole fraction gas.
7.1.3.4 Calculate the indication error according to formula (1) and formula (2).
7.2 Opacity measuring device
7.2.1 Calibration of indication error
Turn on the power. The operator will warm up according to the time specified in
the opacity measuring device manual. After the preheating is completed, adjust
the optical path of the opacity measuring device, to make the opacity measuring
device reach the requested work state as specified in the manufacturer's
manual.
Where:
δv - Relative error of the speed measuring device.
7.3.1.2 Acceleration indication error
a) Install and adjust the standard speedometer according to the use
requirements to make it in normal working condition. Select any three
accelerations within the range of (-1 ~ 2) m/s2 as calibration points, but
there must be a calibration point less than 0 m/s2. The acceleration
calibration points can also be determined according to the actual
conditions of the measured road.
b) According to the calibrated acceleration point, the limit value of the speed
measuring device shall be adjusted appropriately. A standard
speedometer is used to measure and record the actual acceleration value
of the test vehicle when it passes through the monitoring area, whilst the
speed measuring device of the remote sensing system measures the
acceleration of the test vehicle and takes pictures. According to the above
method, the tested acceleration is measured 3 times; the value of each
measurement is compared with the value of the standard speedometer.
c) Acceleration indication error of speed measuring device is calculated
according to formula (9):
Where:
Δα - Acceleration indication error of speed measuring device, m/s2;
α - Acceleration indication value of speed measuring device, m/s2;
α0 - Acceleration indication of standard speedometer, m/s2.
7.3.2 Equal-precision comparison method
When the actual detection road cannot meet the test of the experimental vehicle,
the equal-precision comparison method can be used to measure the speed and
acceleration, that is, the radar-type speed measurement standard device and
the remote measurement system speed measurement device are used for
comparison detection. In the state of real traffic flow, the radar-based speed
measurement standard device and the remote sensing system speed
measurement device simultaneously detect vehicles passing through the
δQY - The indication error of the atmospheric pressure measuring device;
- The average value of 3 indication values of atmospheric pressure
measuring devices, kPa;
- The average value of the indication values of 3 atmospheric pressure
measurements of calibration devices, kPa.
7.5.4 Indication error of wind speed measuring device
7.5.4.1 Place the standard anemometer and the calibrated wind speed
measuring device at the outlet of the same standard wind speed generator; fix
them firmly.
7.5.4.2 Start the standard anemometer smoothly; control the indication values
of the standard anemometer to be about 4 m/s, 5 m/s, 7 m/s, respectively. When
the wind speed is stable, read the indication value of the calibrated wind speed
measuring device. Calculate the indication error of the wind speed measuring
device according to formula (14).
Where:
δCB - The indication error of the wind speed measuring device;
HC - Indicating value of the calibrated wind speed measuring device, m/s;
HB - Indicating value of standard anemometer, m/s.
8 Representation of calibration result
8.1 Calibration data processing
The relative indication error generally retains 2 significant figures.
8.2 Evaluation of uncertainty of calibration results
The uncertainty of the indication error measurement results of the exhaust gas
measuring device, speed measuring device, meteorological parameter
measuring device, slope measuring device is evaluated according to JJF
1059.1. The uncertainty evaluation example of some parameters is as shown
in Appendix D.
Appendix D
Example of uncertainty evaluation of indication error calibration
for remote sensing system of vehicle exhaust
D.1 Evaluation of calibration uncertainty of indication error of gas measuring
device
D.1.1 Measurement method
In accordance with the requirements of this specification, during the calibration
process, a series of standard gases of the same type as the gas measured by
the calibrated measuring device are used to calibrate the measurement
performance of the calibrated measuring device. The indication error is an
important indicator of the measuring device. There are two methods to calculate
the indication error in this specification, one is the absolute error and the other
is the relative error. According to the requirements of this specification, it
analyzes the expanded uncertainty of the absolute error and the relative error
of the gas measuring device, respectively.
D.1.2 Measurement model
D.1.2.1 The formula for calculating the absolute error of the indication:
Where:
ΔC - The absolute indication error of the gas measuring device;
- The average value of 3 measurements at the ith calibration point of the
gas measuring device;
Cs - The molar fraction value of the standard gas.
D.1.2.2 Calculation formula for relative error of indication:
Where:
δC - The relative indication error of the gas measuring device.
D.1.8 The expanded uncertainty of the indication relative error of the CO gas
mole fraction of the gas measuring device
D.2 Evaluation of calibration uncertainty of speed indication error of speed
measuring device
D.2.1 Measurement method
According to this specification, the uncertainty of calibration of the indication
error of the speed measuring device at the target speed of 60 km/h is evaluated.
D.2.2 Measurement model
Where:
Δv - Speed indication error of the speed measuring device, km/h;
v - Speed measurement value of the speed measuring device, km/h;
v0 - Speed value of standard speedometer, km/h.
D.2.3 Variance formula of indication error
In formula (D.4), v and v0 are not related to each other, so
Where:
uc(Δv) - Combined standard uncertainty, km/h;
u (v) - The standard uncertainty introduced by the resolution of the speed
measuring device itself, km/h;
u (v0) - The standard uncertainty introduced by the standard speedometer,
km/h;
u (δ) - The standard uncertainty introduced by measurement repeatability,
km/h.
D.2.4 Evaluation of standard uncertainty
D.2.4.1 Type A evaluation of standard uncertainty
Take the point where the speed value of the speedometer is at 60 km/h. Read
Where:
uc(Δα) - Combined standard uncertainty, m/s2;
u(α) - The standard uncertainty introduced by the repeatability of
acceleration measured by the speed measuring device, m/s2;
u(α0) - The standard uncertainty introduced by the standard speedometer,
m/s2.
D.3.4 Evaluation of standard uncertainty
D.3.4.1 Type A evaluation of standard uncertainty
Take the point where the acceleration of the standard speedometer is 2 m/s2.
Read the indication value of the acceleration of the speed measuring device.
Repeat 6 times under the same conditions. The measured values are 1.9 m/s2,
1.9 m/s2, 2.0 m/s2, 1.9 m/s2, 2.0 m/s2, 1.9 m/s2.
Average...