Application Notes


  1. Base Metal Reading

  2. Measurement Terminologies

  3. Difference between QNix 7500 and QNix 8500 Coating Thickness Gauges



Base Metal Reading

Average Zeroing Preparing the QNix 8500 Coating Thickness Gage

  • Press the Right Arrow –scroll down to “Calibration”
  • Press the Bottom Arrow to “Zero Averaging” and confirm with Right Arrow.
  • Use Upper Arrow to increase, and Lower Arrow to decrease desired number of Zero reference readings. (Maximum - up to 19) the more zero reference readings, the better.
  • Press the Right Arrow to confirm the setting    

          Virtual Zero Reference setting on the QNix 8500 Coating Thickness Gage



  • Press the Upper Arrow and when prompted place probe on blasted surface and when again prompted lift probe about 4 inches away from the surface – you have recorded your first ZRS.

  • This procedure is repeated until the set up number of desired zero references is completed -  The Number of remaining ZRS decreases each time this procedure is carried out – example for 10 ZRR on display in smaller font (10/10/, 9/10, 8/10, 7/10, 6/10, 5/10, 4/10, 3/10, 2/10, 1/10).  

  • Note: When all ZRSs are recorded, coating thickness gage display zeroes in Standard font.

  • Now- A virtual zero reference for that particular blasted surface is set in the coating thickness gage. You are good to go! Start to measure your coating thickness.


Note: Do not forget to repeat this procedure if you are going to measure on a different blasted surface (different blasted profile).


Measurement Terminologies

QNix Coating Thickness Gauges

As you read the instruction manual, technical specifications and work with the QNix Coating Thickness you will come across many terms -accuracy, precision, R&R Test, many of them often used in quality assurance, quality control and international organizations such as ASTM, SSPC, ISO, etc,.Many manufacturers use Gauge accuracy to mean the trueness of the gauge or to define the degree of error that exist between measured data and the actual thickness of the film being measured. Stating the accuracy of a gauge tells us the level of performance and ability of that gauge to measure the actual and true thickness of a coating. Manufacturer specify this accuracy, entirely or split for the measuring range of the thickness gauge. In the case of a two sectioned accuracy statement, the lower measuring range is often more accurate than that of the higher measuring range. Also, a statement of accuracy includes a constant fixed portion across the measurement range and a variable portion related to data for that specific thickness. Here is a typical accuracy statement for a QNix 8500 Paint Thickness Gauge: 

± (1 µm + 2% of the reading) in the range of 0.0 to 2.0 mm,  

± 3.5 % of the reading from 2.0 mm

 Note that gauge accuracy should not be confused with resolution – many use these terms interchangeably. While accuracy expresses the closeness of measurement to the true value, resolution expresses the fineness of the gauge display.

 Not often stated by the manufacturers, precision independent of accuracy. It describes random errors during measurements and the relationship between measurements, mostly referring to the closeness of such measurements. Statistically, it measures the variability or bias. 

Two important constituents of precision in a measurement system are Repeatability and Reproducibility. Repeatability variation caused by the measuring apparatus when used many times by the same operator and the same measuring object under the same conditions. Comparing different device, less variation of measurements means more repeatability. Reproducibility is variation caused by the measurement system. It defines the ability of different operators getting the same readings while measuring the same object, under the same conditions.


Gauge R&R Test is performed due to suspected variances and variations involved in quality systems and manufacturing processes. Quality control departments are interested in knowing the percentage of variance introduced by a measurement system. Examining the repeatability of the gauge and reproducibility of the operator, it is easy to determine the location of variation and to take appropriate measures to improve data quality of the measuring system.

Example of Gauge R&R Test performed at Automation Dr. Nix:




Which Software version should I use for my QNix Coating Thickness Gauge?

You must have a Coating Thickness gauge with memory capability ( QNix 1500M, QNIx 7500M, QNix 8500 B, QNix 8500P). To simplify things, both versions of the software have been included on one CD. To download the CD, make sure the USB interface acble or the wireless USB Dongle is inserted into your USB port. The software will direct you through the download. Choose Version 6.2 for QNix 1500M and QNix 7500M. Choose version 7.2 for QNix 8500.


How do I verify proper installation of the Software Driver?

To verify proper installation of the driver, open the Device Manager (Control panel >System>Hardware>Device Manager). The newly downloaded device appears in the group "Ports". Note that Software version 6.2 can only handle COM Ports 1-4. So if your device is not working, and it is set at say COM Port 5, you will need to change to a lower COM Port. Make sure the chosen Com port is not occupied by another device. If it still does not work, "double click on "QNix USB Com port" in the device manager to get to the properties page. Now choose the Tab called "Port Settings" and then click on "Advanced". You will see all put that are available and which of them is already in use. Choose the port that is not occupied and then press "OK".

 How do I change the Unit of my QNix 7500 Coating Thickness Gauge?

In order to change units you should have a Software and USB interface cable. Haven installed the software, insert USB cable to the USB port of your computer and the other end to the bottom of the gauge – slight the battery cover to access it. Then open the software and click of QuaNix. Go to change unit and click of the desired one and then again click get unit. If problems occur, your cable is probably not inserted properly.

 What is the operating and storage temperature for QNix Coating Thickness Gauge?

Storage temperature  -10ºC - 60ºC  (14ºF-140ºF)
Operating temperature  0ºC - 50ºC ( 32ºF-122ºF)

 What standards and regulations does QNix brand comply to?

Qnix brand complies to DIN 50981, 50984,: ISO 2178, 2360, 2808: BS 5411, 3900-C5: ASTM B499, D 7091.


When and how do I do a Zero-adjustment?

A new zero adjustment is required when using the gauge for the first time, working with different substrates or after inserting new batteries. To zero, place the probe of the QNix on one of the zero reference plates in the carrying case. For ferrous mode, place on ferrous plates and for non ferrous on non ferrous plate. It is better to use your own uncoated substrate to zero. Place the probe and press the red buton or switch. Release and lift the gauge about 4 inch away from the zero reference. Two numbers will appear and the gauge will read zero.

 Why I am having problems zeroing the new version of the QNix 4200/4500 paint thickness Gauge?

Please make sure the probe is switched to the correct measuring mode during zero- adjustment. Otherwise false measurements might occur. Please make sure the probe tip is placed perpendicularly and evenly on the surface of the zero plate or on your uncoated substrate. If the value indicated is not within the range of the basic tolerance, adjust the gauge as follows: Place the gauge on the zero plate (substrate). Then press the button once. A control number appears on the display and an acoustic signal sounds. Now lift off the gauge at least 10 cm (4 inches) from the zero plate (substrate). The acoustic signal sounds again and another control number appears. The zero- adjustment is completed. When repeating measurements on the same spot, the reading may not always be 0 μm or 0.00 mil, since surface roughness, dirt, scratches etc. might cause variances.


Difference between QNix 7500 and QNix 8500 Coating Thickness Gauges

QNix 7500 Basic Qnix 8500 Basic
  • Modular, precise measurements for all QNix probes.
  • All Fe and NFe probes can be inserted directly into gauge or through adaptor cable.
  • High precision over the entire measuring range (up to 200 mil FE & 80 Mil NFE)
  • No calibration.
  • Automatic On / Off.
  • R-S 232-Interface for on-line measurements.
  • Modular, precise measurements for all QNix probes.
  • All Fe and NFe probes can be inserted directly into gauge or through adaptor cable.
  • High precision over the entire measuring range (up to 200 mil Fe & 80 mil NFE)
  • No calibration.
  • Automatic On / Off.
  • USB Interface for on-line measurements. Set Limits (Lower & Upper) Data Memory –up to 100 ReadingsCalculate Average, SD, Max, Min. Set One batch. One custom calibration. Backlight.Normal or Flip Display


My QNix 8500 is showing dubious readings – what could be the reason?

Please check for the following:

  1. 1. Does your display show the correct substrate?
  2. 2. Are you zeroing on a dual mode – see dual signal on display.
  3. 3. If problem persists, reset gauge by removing batteries. Then set mode of gauge to single mode before zeroing.


I need to update the QNix 8500 Thickness gauge version Firmware?

Please go to and download the newest version.


What does this Display message mean?

Fe= measurement on iron or steel substrate

NFe= measurement on non-iron metal

Zero Reference Error = zeroing error or handling error

INFI= wrong substrate, reading beyond measuring range

low battery, have new ones ready= low battery, have new ones ready

low or empty battery= low or empty battery

automatic substrate selection activated= automatic substrate selection activated


Do I require an RMA to send a QNix coating Thickness Gauge to TestCoat for repair?

An RMA is NOT required. Simply send your gauge to us with a delivery note indicating the address, gauge type and a short description of the problem.


Where do I send my QNix paint thickness gauge for repair or recertification?

TestCoat Inc. Attn: Service Department 324 East 11th Street, Ste B 2 Tracy, CA 95376 USA

 How long will my order take to arrive?

Standard orders will be shipped within 3 business days of order receipt.


How much does shipping/freight cost?

Shipping within USA is $3.50 by post. Standard courier charges are $15.00. Priority overnight shipment (order needs to be received before 1:00 pm) costs $45.00. Please contact us for international shipping.