The National Pressure Measurement Technology Committee is in charge of the explanation of this regulation.
Introduction
JJF1001 General Terms in Metrology and Their Definitions, JJF 1002-2010 The Rules for Drafting National Metrological Verification Regulation, and JJF 1059.1-2012 Evaluation and Expression of Uncertainty in Measurement, etc., jointly constitute the basic series of specifications for the revision of this regulation.
In addition to editorial changes, the following main technical changes have been made with respect to JJG 971-2002 Verification Regulation of the Liquid Level Measuring Devices:
——as required in JJF 1002-2010 that the Instruction shall be necessary, the Introduction is added.
——the terms are adjusted. The terms "set point error", "differential value" and "differential gap" are deleted, and the terms “level” and "liquid level gauge" are added.
—— the application occasions of liquid level gauge are specified in the clause “General”. According to the current industry customs, four classification methods are proposed: liquid level measurement method, liquid level gauge measurement method, liquid level gauge installation method and liquid level gauge measurement principle.
——the content of type evaluation is deleted from the metrological performance requirements and general technical requirements.
——in the verification method, horizontal liquid level simulation verification device is put forward, and the basic technical requirements are proposed. New technical requirements are put forward for the original vertical liquid level verification device.
——the verification process and requirements of the two kinds of devices are specified in the verification method.
——the contents of Annex A "Type Identification or Prototype Test Items and Test Methods" in the original regulation are deleted.
—— Annexes B and C of the original regulations are modified accordingly.
The previous edition of this specification is as follows:
——JJG 971-2002
Verification regulation of liquid level gauges
1 Scope
This regulation is applicable to the initial verification, subsequent verification and in-service inspection of liquid level gauges (excluding radiation level gauges). The calibration of level gauge can refer to this regulation.
2 Normative references
The following document is referenced in this regulation:
JJG 882 Pressure Transmitters
For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
3 Terms and meteorological units
3.1 Terms
3.1.1 level
generic term of liquid level, material level and interface (position) is a parameter reflecting the total amount of objects and the surface characteristics of materials
3.1.2 liquid level gauge
Instruments used to indicate and control liquid level and interface (position) in industrial process measurement and control system
3.2 Measurement unit
The legal measurement unit used by level gauge is m (meter), or its decimal multiple unit: mm, cm, etc.
4 General
Liquid level gauges are widely used to measure the internal liquid level or interface of tanks, kettles, towers, bottles, furnaces and canals in industrial processes.
The liquid level measurement methods include visual method, manual measuring method, blowing method, force measuring method, pressure method, electrical characteristic method, reflection method, thermal method, radiation method, neutron method, etc.
Liquid level gauges can be divided into contact type and non-contact type according to the measurement mode, can be divided into top-mounted, side-mounted, top-bottom, side-side, side-bottom, top-side and side-wall types according to installation modes, and can be divided into communication type, buoyancy type, pressure type, reflection type and electrical characteristic type according to the measuring principle.
Communication type: (quartz) glass tube level gauge and glass plate level gauge;
Buoyancy type: magnetic column (plate) level gauge, magnetostrictive level gauge, servo level gauge, steel strip level gauge, (electric) buoy level gauge and floating ball level gauge;
Pressure type: static pressure (input) level gauge (transmitter) and differential pressure level gauge (transmitter);
Reflection type: radar level gauge, ultrasonic level gauge and guided wave radar level gauge;
Electrical characteristics: radio frequency admittance level gauge, capacitance level gauge, etc.
Introduction I
1 Scope
2 Normative references
3 Terms and meteorological units
4 General
5 Metrological performance requirements
6 General technical requirements
7 Control of metrological instruments
Annex A Verification record format of liquid level gauge
Annex B Inside page format of verification certificate/verification result notice
