CoverMaster CM9 cover meter
User Verification of Calibration

Standard Head:

Required:

A set of ribbed high-tensile reinforcing bars, of diameters 8, 10, 12, 16, 20, 25 and 32mm (or as desired, but including T16), all of length 500mm (minimum);
A set of spacers, ideally of machined ABS, of thicknesses 20, 30, 35, 40, 60 and 80mm (or as desired, but including 35mm).

Procedure:

Connect the standard search head to the CM9, and switch on.
Position the search head face upwards on a wooden table.

From the Main Menu, select and enter the "Dep." mode, and zero the instrument.
For every individual measurement (unless stated otherwise), the sub-procedure is:

Place the appropriate spacer on the face of the search head;
Check that the diameter shown is that of the bar to be measured (changing if necessary);
Zero the instrument;
Place the bar on the spacer centrally above the search head and parallel to its long axis;
Record the reading(s) indicated.

Note that, for the purposes of these procedures, the instrument is required to be zeroed immediately before each reading.

The specific tests below ("Tables") all refer to the example Calibration Certificate .

Table 1 (T16 bar at various covers):

Perform the sub-procedure using the 16mm diameter bar and spacers of 20, 30, 40, 60 and 80mm (there should be no need to alter the diameter setting).
The indicated reading to be recorded is the "known diameter" cover (in "jumbo" digits).
The permitted tolerance is ±2mm for covers/spacers of <40mm, and ±5% for covers/spacers >40mm.

Table 2 (various bar diameters at 40mm cover):

Perform the sub-procedure using the 40mm spacer and bars of diameters 8, 10, 12, 16, 20, 25 and 32mm (the diameter setting will need altering to suit each measurement).
The indicated reading to be recorded is the "known diameter" cover (in "jumbo" digits).
The permitted tolerance is ±2mm.

Table 3; rows one and two (Autosizing various bars at 35mm cover):

Perform the sub-procedure using the 35mm spacer and bars of diameters 8, 10, 12, 16, 20, 25 and 32mm (the diameter setting is irrelevant).
The indicated readings to be recorded are the "Autosize" values for diameter and cover (the values indicated in parentheses); the main "jumbo-digits" indication is to be ignored.
The permitted tolerance in diameter is ±2 bar-sizes, ie a T16 bar is allowed to indicate anywhere between 10mm and 25mm inclusive.
The permitted tolerance in cover is ±2mm.

Table 3; row three (Orthogonal-sizing of various bars at 35mm cover):

Return to the Main Menu, and select and enter the "Size" mode.
Measurements are made with the same 35mm spacer and range of bars as in the first two rows of Table 3 (above).
Refer to the User Manual for fuller details of the Orthogonal bar-sizing method.
The CM9 will require you to zero the instrument before each measurement.
Place the bar on the spacer aligned parallel to the long axis of the head (as usual) and take the "Para" reading; then rotate the bar to be at right angles to the long axis of the head, but still crossing above the centre of the head, and take the "Orth" reading.
Observe the values of diameter and cover displayed, and record the diameter value.
The permitted tolerance in diameter is ±1 bar-size, ie a T16 bar is allowed to indicate anywhere between 12mm and 20mm inclusive.

Permitted tolerances in cover in Tables 1 and 2 are those in British Standard BS1881:204.
That standard permits errors of ±5mm in cover in Table 3 row 2; and does not specify any requirement for diameter-determination (Table 3, rows 1 and 3).

Large Head:

The CM9 is supplied factory-calibrated for optimum accuracy with the standard head; the large head is available as an accesssory to increase detection depth.
The performance and accuracy of the large head can be monitored in a similar way as described below; and if any results are obtained which are outside the suggested limits, they should be recorded as "corrections to be applied", but not as a failure to meet specification.

(1) Single bar at various covers:
Use a bar of T16, T20 or T25 (with diameter set accordingly), and spacers of 40, 60, 80, 120 and 160mm; follow the earlier sub-procedure.
Expect cover accuracies of ±5%.

(2) Various bars of known diameter at one cover:
Use a spacer of 80mm, and follow the earlier sub-procedure.
Expect cover accuracies of ±4mm.

(3) Various bars of unknown diameter:
Use a spacer of 70mm, and follow the procedure for "Table 3" earlier.
Expect cover accuracies of ±5mm. Expect diameter accuracies of ±2½ sizes using "AutoSize" and ±1½ sizes using "Orthogonal".

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Protovale CoverMaster CM9 cover meter

Calibration Certificate No. __________

CoverMaster CM9 cover meter: serial no. _________ , software vsn. ______

Table 1: Measurement of cover to T16 bar
Actual cover	Indicated cover	Permitted limits		Units
Actual cover	Indicated cover	minimum	maximum	Units
80		76	84	mm
60		57	63	mm
40		38	42	mm
30		28	32	mm
20		18	22	mm

Table 2: Measurement of 40mm cover (permitted tolerance ±2mm)
Bar diam.	8	10	12	16	20	25	32
Indicated cover

Table 3: Bar-sizing at 35mm cover (showing permitted* tolerance)
Actual bar diameter	8	10	12	16	20	25	32
AutoSize diameter								± 2 sizes
AutoSize cover								± 2 mm.
Orthogonal diameter								± 1 size

* BS1881:204 only applies to bars of known size (Tables 1 and 2), and permits ±5mm in cover in Table 3; no Standard exists for bar-sizing.

Performance Certified to comply with the requirements of British Standard BS1881:204:1988 "Recommendations on the use of electromagnetic covermeters" and also with the requirements of Standards BS8110, DIN1045 and EC2.

Date:
Authorised signatory:

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CoverMaster CM9 cover meter User Verification of Calibration