ISO 19840

Instruction Manual Addendum
(Advanced Models Only)

This addendum to instruction manual v8.0 is intended to provide support for the ISO 19840 feature found in all PosiTector 6000 Advanced models with serial numbers greater than 864000.

How to use the PosiTector 6000's ISO 19840 mode...

Step 1: Create a New 19840 batch

1A. Select the Memory option from the gage menu as shown.
1B. Select the New 19840 option from the Memory menu.

Step 2: Adjust 19840 parameters as necessary

2A. Review the four parameters.

To adjust a parameter use the up and down buttons to move the highlighting bar to the appropriate parameter, then use the (+) and (-) buttons to adjust that parameter.

2B. Adjustable Parameters

NDFT (Nominal Dry Film Thickness): the dry film thickness specified for the coating system. Adjust the displayed value up (+) or down (-). Alternatively, measure a coating with a thickness close to the required value and make final adjustments with the (-) (+) buttons.

MAX NDFT (Maximum NDFT):  the specified maximum thickness value for the structure. This value should be that thickness above which adverse performance characteristics appear, such as mudcracking, embrittlement, solvent retention, loss of adhesion, cohesive splitting, etc. Adjust the displayed value up (+) or down (-). Alternatively, measure a coating with a thickness close to the required value and make final adjustments with the (-) (+) buttons.

Use MAX NDFT [  ]:  select this option if each individual measurement cannot exceed the MAX NDFT value.

NOTE: If a maximum thickness value is not specified, set the MAX NDFT value to 0 using the (-) button and uncheck Use MAX NDFT.

Min # Measurements:  develop a Sampling Plan to determine the minimum number of readings required per unit area. Adjust the displayed value up or down using the (-) (+) buttons.

Table 1 in ISO 19840 outlines a Sampling Plan that determines the number of measurements that shall be taken in a designated inspection area, based on the size of that area. Provided that a coated structure has not been divided into individual inspection areas, the entire structure should be considered as the inspection area for measuring the coating thickness.
Coated welds, corners, edges, fixtures, etc. may require special consideration with regards to coating thickness measurement. The procedure for inspecting these measurement areas will be agreed upon by all interested parties.

Step 3: Take measurements

Begin taking measurements on the coated surface in the measurement area. With each measurement the following occurs:

  • The gage beeps twice (when sound is enabled in the Setup menu) and the current reading is displayed next to the corresponding reading number.
  • The batch information is updated with Pass or Fail to determinations based on the following ISO 19840 requirements:
  1. The minimum number of measurements as specified in the Sampling Plan shall be taken
  2. The average of all the individual dry-film thicknesses shall be equal to or greater than the nominal dry-film thickness (NDFT)
  3. All individual dry-film thicknesses shall be equal to or above 80% of the NDFT
  4. Individual dry-film thicknesses between 80% of the NDFT and the NDFT are acceptable provided that the number of these measurements is less than 20% of the total number individual measurements taken
  5. All individual dry-film thicknesses shall by less than or equal to the specified maximum dry-film thicknesses, if specified

If all batch criteria are not met, as indicated by the presence of a Fail – the inspection area is rejected.

Repeats: If an individual measurement value does not meet the above criteria 3 or 5, the reading can be rejected by pressing the (–) button. After rejection, take a repeat measurement within 10 mm of the location where the rejected reading was taken. If the repeat measurement does not meet the criteria, it cannot be repeated again. The maximum number of repeat measurements allowed in the batch is determined according to the Sampling Plan.

The number of repeat readings taken and the total number of available repeats are displayed.

Step 4: Review results

There are 5 options for reviewing the ISO 19840 batch results:

  1. Download the batch to PosiSoft Desktop.
  2. Transfer the batch to the PosiTector App.
  3. Upload the batch to PosiSoft.net.
  4. View and print the batch using PosiSoft USB Drive.
  5. Print the batch report using the optional Bluetooth Printer.

In each of the above options, all ISO 19840 batch information is presented: probe serial number, 19840 parameters, batch criteria, Pass/Fail conclusions and individual measurements with time and date stamp.


  1. Select the Delete option from the Memory submenu to erase a batch or the entire contents of the PosiTector menu.
  2. Select the Close options for the Memory submenu to end the current 19840 analysis but retain all existing batch measurements.
  3. 19840 parameters are unaffected by performing a gage Reset from the Setup menu.
  4. A Hard Reset will delete all 19840 parameters and restore the gage back to factory settings.

The PosiTector 6000 ISO 19840 feature is intended to support the 19840 Standard, not replace it. It is the responsibility of the user to read and understand the document, and to verify the accuracy of the gage's conclusions.

What is ISO?

Founded in 1947, the International Organization for Standardization (ISO) is an independent, non-governmental organization, the members of which are the standards organizations of the 165 member countries. It is the world's largest developer of voluntary international standards and it facilitates world trade by providing common standards among nations. More than twenty thousand standards have been set, covering everything from manufactured products and technology to food safety, agriculture, and healthcare.

Observing ISO standards aids in the creation of products and services that are safe, reliable, and of good quality. The standards help businesses increase productivity while minimizing errors and waste. By enabling products from different markets to be directly compared, they facilitate companies in entering new markets and assist in the development of global trade on a fair basis. The standards also serve to safeguard consumers and the end-users of products and services, ensuring that certified products conform to the minimum standards set internationally.

What is ISO 19840?

ISO has developed a series of Paint Application Standards, Guides and Specifications. One of them is entitled, "ISO 19840:Paints and varnishes – Corrosion protection of steel structures by protective paint systems – Measurement of, and acceptance criteria for, the thickness of dry films on rough surfaces” (click here to purchase the document).

19840 describes the procedures used to measure the thickness of a dry film of a nonmagnetic coating applied on a magnetic substrate using commercially available magnetic gages. However the described methodology can be used by most non-destructive coating thickness gages including those using eddy-current or ultrasonic principles.

The standard defines a procedure to determine if the film thickness over an extended area conforms to the minimum and the maximum levels specified.


There are several ways to evaluate film thickness with the PosiTector 6000...

  1. Take a single measurement.
  2. Calculate the average of several measurements -- the PosiTector 6000's Statistics mode.
  3. Analyze a larger area using a statistical approach in accordance with IMO -- the PosiTector 6000's 90/10 mode.
  4. Analyze a larger area using a statistical approach in accordance with SSPC -- the PosiTector 6000's PA2 mode.
  5. Analyze a larger area using a statistical approach in accordance with ISO -- the PosiTector 6000's 19840 mode.

A large surface usually cannot be characterized accurately by a single measurement. Variations in substrate preparation, painting technique, measuring technique, etc. require an analysis of several measurements taken over a large portion of the surface.

The PosiTector 6000's statistics mode displays individual measurements AND maintains a running average value. It also displays minimum and maximum values.

ISO has taken this a step further by developing a specification for structural steel painters. Known as ISO 19840, this specification has become widely used both inside and outside the structural steel painting industry.

ISO 19840 helps determine if film thickness over an extended area conforms to user-specified minimum and maximum levels.

The sampling plan used in ISO 19840 states that if the structure is divided into individual “inspection areas” as defined in ISO 12944 Part 7 and Part 8 , then these areas are tested. “Inspection areas” are separate areas on the structure used to establish a minimum acceptable standard for the work, and are typical areas of the structure where tests are carried out to ensure conformance with the specification.

If such areas are not identified, then the whole structure is considered as the inspection area. In the latter case, requirements for flat areas are as follows.

  • 5 spot measurements in the first square meter
  • 10 spot measurements for 1 to 3sq m
  • 15 spot measurements for 3 to 10sq m
  • 20 spot measurements for 10 to 30sq m
  • 30 spot measurements for 30 to 100sq m
  • 10 spot measurements for each additional 100sq m

ISO 19840 does allow for an increased number of measurements to be made on areas having difficult configurations, such as stiffeners, brackets, and supports. The standard also provides guidance for the number of measurements that can be repeated if an individual measurement is not within specification.

Advanced models of the PosiTector 6000 have a 19840 mode that helps the user collect measurements in conformance with the ISO 19840 standard. Then, based on user-set parameters that include the target thickness, the gage indicates a Pass or Fail condition.

How does the gage do this?

The PosiTector 6000 has on-board memory into which all measurements are stored. Individual measurements are monitored by the gage and used to perform calculations to determine Pass/Fail criteria in accordance with ISO 19840 for the batch.

Statistics Mode

PosiTector 6000 Standard and Advanced models have a Statistics mode. When selected, the gage continuously updates running average and standard deviation calculations. Maximum and minimum values are also tracked while measurements are being taken.

The last measurement can be deleted with the (-) button, while the (+) button clears all statistics.


Is it possible for all the individual measurements to PASS but for the batch to FAIL?

Yes. If the measurement value of more than 20% of the individual readings are between 80% of the NDFT and the NDFT, the criteria is not met and the batch will Fail.

Is it possible to change PASS/FAIL criteria after all measurements have been taken?

No. Once the ISO 19840 criteria has been set, the parameters cannot be altered. Select a New 19840, enter the desired criteria and repeat the measurements. 

Can I delete a bad measurement?

Yes. Use the (-) button to delete the last measurement taken. Each measurement can only be repeated once. The maximum number of repeat measurements allowed in the batch is determined by the Min # Measurements.

Must I specify both a minimum and a maximum thickness?

For many coatings used today it is a good practice to specify both. This range is usually obtained from the coating manufacturer's technical data sheet. But, economic factors along with flow characteristics of the coating usually control excessive film build, so it is common to specify only a minimum thickness. When only a single target value is available, set the NDFT to that value and set the MAX NDFT to 0 and uncheck Use MAX NDFT.