Dynamic Measuring System for Liquids (Other than Water)
Part IV of the Eighth Schedule of the Legal Metrology (General) Rules, 20101

Part 1: Terminology

Meter

An instrument intended for measuring continuously, memorize and display the volume of liquid passing through the measurement transducer at metering conditions.
Transducer is a device that converts mechanical signals to electronic signals for the calculator.

Measuring System

The meter with all ancillary and additional devices will constitute a measuring system.

Ancillary Devices

Zero-setting Device
Volume Indicating Device
Printing Device
Memory Device
Price Indicating Device
Totalizer
Correction Device
Conversion device - a device to convert a volume into a mass.
pre-setting device
self-service device

Metrological Characteristics

Absolute Error

The result of a measurement minus the true value of the measurand
(a quantity that is being determined by measurement).
E_abs = V_d − V_t E_abs = Absolute Error V_d = Value Displayed V_t = True Value.

Relative Error

The absolute error divided by true value of the measurand.
E_rel = E_abs / V_t

Maximum Permissible Error

The extreme values permitted by the specification for an error.

Minimum Measured Quantity

The smallest volume of liquid for which the measurement is metrologically acceptable for that system.

Minimum specified volume deviation

The absolute value of the maximum permissible error for the minimum measured quantity of a measuring system.

Intrinsic error

The error of a measuring system used under reference condition.

Part 2: General

Field of Application [1(2)]

Liquids to be measured

Petroleum and related products diesel, crude oil, lubricants, LPG etc.
Liquid food - milk, cream, alcoholic and non-alcoholic beverages, soft drinks, vegetable oils etc.
Alcohol
Chemical Products like Acids, ammonia-solutions etc.
All other liquids excepts drinking cold water and hot water but including distilled water and de-ionized water.

Field of Operation [2(3)]

Characteristics required to be known for verification of a measuring system.

minimum measured quantity
minimum flow rate Q_min and maximum flow rate Q_max
minimum pressure P_min and maximum pressure P_max of the liquid
dynamic viscosity of the liquid
minimum temperature T_min and maximum temperature T_max of the liquid
environmental class.

Environmental Class

Measuring systems are divided into three classes according to climatic and mechanical environmental conditions:

class B for fixed instruments installed in a building,
class C for fixed instruments installed outdoors,
class I for mobile instruments, in particular measuring systems on trucks.

This information is required for severity test to be done during model approval. However, the OIML has withdrawn the classification.

Accuracy Classes [2(4)]

Classification of the measuring devices under this heading is based on their field of application, and not on the degree of accuracy.

Class	Field of Application
0.3	Measuring Systems on Pipeline
0.5	Fuel dispensers for motor vehicles (Except LPG dispensers) Measuring Systems on Road Tankers for liquids of low viscosity (≤ 20mPa.s) like milk (3) Alcohol, Isopropyle (2.4)) Measuring system for unloading of ship/ rail/ road tankers Measuring system for milk Measuring system for loading ships Measuring system for refueling aircraft.
1.0	Measuring system (except LPG) for liquified gases at temperature ≥ - 10´C· LPG dispensers for motor vehicles.
1.5	Measuring system for liquified carbon dioxide.

Maximum Permissible Error [2(5)]

Maximum Permissible Relative (?) Error (±) for volumes two litres and above
Apparently, the use of term 'relative' was a mistake. Table 3 does not bear the term. The OIML omitted the term in 2007 edition.

Table 2

	Accuracy Classes
	0.3	0.5	1.0	1.5
Line A	0.3 %	0.5 %	1.0 %	1.5 %
Line B	0.2 %	0.3 %	0.6 %	1.0 %

Line A: applicable to whole measuring system
Line B: applicable to metering unit for type approval

Maximum Permissible Error (±) for volumes below two litres

Table 3

Measured Quantity	Maximum Permissible Error
from 1 to 2 L	value fixed in Table 2, applied to 2 L.
from 0.4 to 1 L	twice the value fixed in Table 2
0.2 to 0.4 L	twice the value fixed in Table 2, applied to 0.4 L
from 0.1 to 0.2 L	4 times the value fixed in table 2
less than 0.1 L	4 times the value fixed in table 2, applied to 0.1 L

* In the above table, the quantities 1 l and 0.4 l have been mentioned in two rows which may be confusing.
* The OIML has used the term (applied to Minimum Measured Quantity, MMQ for E_min calculation) for clarification in 2007 edition.

Calculating Maximum Permissible Error

The MPE of a complete measuring system will be the greater of following two values:

absolute value of MPE given in Table 2 or 3
minimum specified volume deviation E_min

Calculating E_min and MPE

Case I: When the minimum measured quantity of the dispenser is 2 litres or more

E_min = 2V_min X A / 100 [A is the numerical value of line A in Table 2]
A diesel dispenser has a minimum acceptable volume capacity of 5 litres, say. Then
E_min = 2 x 5000 x 0.5 / 100 = 50 ml.
This dispenser delivers, say, 50 litres of diesel to a vehicle. Then,
Absolute MPE = 50 x 1000 x 0.5/100 = 250 ml
MPE is 250 ml.

Case II: When the minimum measured quantity is less than 2 litres

E _min = 2 x value given in Table 3 and related to Line A of Table 2
A dispenser has a minimum acceptable volume of 0.5 litre and it delivers 1 litre fuel to a scooter.
E_min = 2 x 2(000) x 0.5 x 0.5/100 = 10 ml [for 1 l, the MPE scales is twice the value fixed in Table 2]
Absolute MPE, from Table 3 is 2 x 1000 x 0.5/100 = 10 ml.
MPE is 10 ml.

It is not permissible for a dispenser to sell quantities less than the declared Minimum Measured Quantity. This declaration will be available on the display panel or the data plate. However, it is not prescribed what action may be initiated against an offender.

Applicability of of Maximum Permissible Error

Rule 2(6)

Maximum permissible errors in line A of Table 2 apply to complete measuring systems, under rated operating conditions, without any adjustment between the various tests, for:

type approval,
initial verification,
subsequent verifications.

Important!

When verifying a dispenser at user level, the whole measuring system will be checked for accuracy which should be within MPE
MPE = Class / 100.
For calculating MPE for 0.5 class instruments.
Convert the volume into mililitre and multiply by 5/1000.

EXAMPLE:
Volume Dispensed: 15 litre = 15,000 ml.
MPE = 15000 X 5 / 1000 = 75 ml.

Statutory Markings

Rule 2(19)

Each measuring system shall bear, placed together legibly and indelibly on the dial of the indicating device or on a data plate, the following information:

General

pattern (model) approval sign
manufacturer's mark
designation of the system
serial number and year of manufacture
class, if other than 0.5

Characteristics

minimum measured quantity V_min
minimum flow rate Q_min and maximum flow rate Q_max
minimum pressure P_min and maximum pressure P_max of the liquid
dynamic viscosity of the liquid
minimum temperature T_min and maximum temperature T_max of the liquid
environmental class.

Sealing and Stamping

Rule 2(20)

Normally, lead seals will be used which should be easily accessible.

Sealing should be provided on all parts of the measuring system which cannot be materially protected in any other way against operations liable to affect the measurement accuracy.
It must be prohibited to change parameters which participate in the determination of the results of measurement, correction and conversion parameters particularly, by means of sealing devices.
In case of measuring systems used for potable liquids like milk, the sealing shall allow dismantling of equipments for cleaning purposes.

Electronic Sealing

When access to parameters that participate in the determination of results of measurement is not protected by mechanical sealing, the electronic sealing may be used.

In case of direct selling to the public, access should be protected by a password as well as a hard key.
The password or code should be allowed to authorized persons only.
It must be possible to, at least, the last intervention to be memorized which shall be stored for minimum of two years and the record shall include -
date and a characteristic element identifying the authorized person making the intervention.

Stamping

The stamping should be made on a permanently fixed Stamping Plate to be provided. Alternatively, it may be made on the Marking Plate.

Dynamic Measuring System for Liquids (Other than Water)Part IV of the Eighth Schedule of the Legal Metrology (General) Rules, 20101