Talk to us:(630) 543-3747

USA
English (US)

Calibration-Explained

Table of Contents

Calibration Explained What is Calibration? The Calibration Process Recalibration How Often Do I Need to Recalibrate? Replaceable Sensors What Are Replaceable Sensors? Replaceable Sensor Benefits Dickson Calibration Why Choose Dickson? Dickson's Calibration Options FAQ Why Should I Calibrate? Who Says What is Accurate? What Does NIST Traceable Mean? What is a 1-Point Calibration? What is a 3-Point Calibration? What is a Span Adjustment? When Does My Calibration Expire?

Calibration Explained

What is Calibration?

THE FUNDAMENTALS

A calibration is a comparison between two measurements. Dickson’s calibration lab compares a device (unit under test) with a more accurate device (the standard). The standard tells us exactly where 70F, 0C, 137F, etc. are. After the comparison is made we adjust the device under test so it reads the same as the standard. At the end of all of that, we do one last check at one or multiple points to fully guarantee the device is within its specified accuracy.

THE DETAILS

Calibration is essential to all devices that measure a variable. However, we often get the questions, “Why isn’t it accurate already?” Isn’t it made to be accurate? The answers are: it is, and yes. However, while our devices are accurate without calibration, we can’t be positive they are accurate to a specific measurable degree (and thus can’t prove their accuracy) unless we perform a calibration. We wish it was as simple as “Yes, this device is accurate,” or “No, this device is not accurate,” However, measuring temperature, humidity, and pressure are delicate sciences. As stated above, a calibration is a comparison between two measurements, and then the subsequent adjustment of one of the measurements if the two measurements are not reading the same value. When you need to calibrate your device, Dickson places it and a standard in a special temperature chamber that allows us to change the environment your device and the standard reside in. We then set the temperature, humidity or pressure values of the chamber using the standard’s measurements. If your device reads the same as the standard, then it is good to go and accurate! If it does not, then we have to adjust its measurements to better match the standard. Dickson will run through this process multiple times, or until the device is as accurate as it is supposed to be (within specification or within “spec”). Once we are sure that your device is accurately measuring temperature, humidity, or pressure, we send it back to you with documentation.

DOCUMENTATION

Over the years, especially with the creation of environmental monitoring regulations for a never-ending list of industries, calibration has become synonymous with documentation. It’s no longer enough for calibration labs to tell you that the device you are purchasing has been calibrated, it must be a documented process that you can point to whenever your devices are called into question. The documentation you receive from Dickson comes labeled as a Certificate of Calibration. This document will tell you at what points Dickson checked your device (at the end of the calibration process) for its accuracy. Depending on the type of calibration you ordered from Dickson, the certificate will display 1 or 3 checked points (shown in values of Fahrenheit or Celsius). These documents will also tell you standard your device was compared to and how accurately your device measures temperature, humidity, or pressure.

The Calibration Process

The calibration process changes depending on the variables you are measuring and the calibration labs performing the calibration. At Dickson, we have SOP’s in place for every unit that goes through a temperature, humidity, temperature and humidity, and pressure calibration, to ensure units are calibrated to as accurate a degree as we have specified. Our process works like this:

A. WE PLACE THE SENSOR AND A STANDARD IN A STABLE ENVIRONMENT

We say “sensor” above to distinguish some of our devices from others. The “sensor” is what is actually taking the temperature, humidity, or pressure. Sometimes that sensor is within the device, making the device synonymous with its sensor. However, other times, like in the case of our Replaceable Sensors, this is not the case, as the sensor is able to be removed from the device and calibrated on its own. “Stable environments” are essential to calibrations. We can’t assume any temperature, humidity, or pressure value without the use of a standard and confined, stable environment. These environments are chambers, where temperatures can be changed quickly and to the exact value we desire.

B. WE COMPARE THE SENSORS READINGS TO THAT OF THE STANDARD ACROSS A RANGE OF TEMPERATURES

After the sensor and standard are both within the stable environment, we run comparison tests for the entire range of temperatures that a sensor can read, recording by how much the sensor deviated from the standard at each temperature value.

C. IF THERE ARE ANY DIFFERENCES BETWEEN THE SENSOR AND THE STANDARD, WE ADJUST THE SENSOR TO ALIGN WITH THE STANDARD

If your sensor isn’t reading temperatures, humidity, or pressure values accurately, we want to fix it. After the comparison is made across the spectrum of temperature, humidity, or pressure values, we take a look at how far off your sensor was off from our standard. If the device is out of its stated accuracy, we adjust it. How do we adjust the sensor? We don’t physically adjust it any way-bending, tearing, taping doesn’t happen-we promise. Instead, we adjust the readings it is sending to the data logger or chart recorder. We want to keep your sensor intact, so we simply adjust the values (via an advanced software system) that it believes it is reading, to account for the miscue in its accuracy. At Dickson, we use two types of adjustments when making your sensor read more accurately. Before we get to them however, it’s important to understand that your device is calibrated on a curve. How we manipulate that curve determines how we get your sensor to be within its accuracy specifications. Zero Adjustment: A zero adjustment is also called an offset. All of Dickson’s units are calibrated on a curve. The zero-adjustment moves that curve up or down to equal what the standard is reading. If your standard reads 26F, but the device displays 24F, your device is off by 2F. You need to adjust the device two degrees in order for it to read accurately. A zero adjustment will shift the entire scale by 2F even if the extreme ends of the scale were not off by 2F. Span Adjustment: A span adjustment is when you adjust the slope of the calibration curve. In the example above, we’d adjust the device by 2F at 24F, but the extremes wouldn’t need any adjustment and therefore would be relatively unaffected.

D. WE RUN THOUGH THE ABOVE PROCESS MULTIPLE TIMES, EACH TIME ADJUSTING THE DEVICE AS IT IS COMPARED AT MULTIPLE TEMPERATURES (MORE ON THIS BELOW, TOO)

We don’t just run through the process once-we do it over and over again until the unit is within our specifications. Because we perform both a zero-point and span adjustment, sometimes multiple calibrations and adjustments are needed to ensure device accuracy.

E. WE PERFORM A FINAL CHECK OF ONE OR MORE POINTS (DEPENDING ON YOUR ORDER) AND CREATE THE NECESSARY CALIBRATION CERTIFICATE

This final check and subsequent documentation is exactly what many of our customers are looking for. When we perform the final comparison and calibration, we generate a document based on how many calibration points you would like to be validated as accurate by us. While we ensure that all units calibrated are within a stated specific accuracy, some industries need proof of that. So, we offer documentation generated from this final check. That documentation will state that the unit has a specific temperature, humidity, or pressure accuracy at a certain temperature, humidity, or pressure. We label that document a “Certificate of Calibration.” For hospitals, pharma manufacturers and distributors, and those in the food industry, auditors may show up and ask to see that document, so having it is probably a good idea. When you are ordering a calibration from Dickson, you have the choice to choose between a 1-point, 3-point, or customer points calibrations. The Certificate of Calibration will reflect which option you choose. For many industries, a 1-point calibration is plenty. As a fair warning, we will usually perform the final check at room temperature, if you are monitoring at a specific temperature that is not between 60-80F, you may want to have a custom calibration point done. We offer a 3-point calibration for those industries who want or need documentation of accurate readings across a larger range. We will typically do a high, middle, and low calibration check across the temperature spectrum that your sensor or probe monitors. For a simple digital ambient sensor, this would be from -20 to 120F. Our custom calibrations are for those organizations who want to see documentation that a validation check was done at a specific temperature. If you know what temperature you will be monitoring at a custom point calibration may be the best documentation for you.

Recalibration

Recalibration is just a calibration for a second time. Your temperature, temperature and humidity, or pressure sensor becomes less and less accurate over time, and eventually, you need to “Recalibrate” it to get it back within its specified temperature accuracy. Due to natural wear and tear, temperature and humidity sensors lose their pinpoint accuracy. Environmental factors such as dust, dirt, and humidity can negatively affect a sensor’s accuracy. This is called drift. These devices probably won’t read 95F in a refrigerator that feels cool, but they may be off by a few degrees. When you calibrate your device you are accounting for the natural drift of the sensor. Those few degrees matter to a lot of organizations and a lot of industries, so we at Dickson recalibrate our manufactured devices in our A2LA accredited laboratory.

How Often Do I Need to Recalibrate?

To determine how often you need to recalibration, consider the following factors:
  • Environment: The more extreme the conditions (really hot or really cold) the more likely the device will drift over time. Dust, dirt, moisture, air particles can all contribute to a device needing to me recalibrated more often as well
  • SOPs: Your standard operating procedure (SOP) may require you to recalibrate more often than our recommendation
  • Regulations: Different industries are subject to different regulations and may require calibrations more or less often than our recommendation. It is best to check with your regulatory agency
  • Auditors: Some auditors have their own preferences on how often a device should be calibrate. Most often they adhere to the regulations for their industry/regulating body, but this isn’t always the case. Be sure to ask them what they’ll be expecting
  • Physical Damage: Dropping, kicking, bumping, or otherwise damaging your device may mean it will need to be recalibrated more often.
You can also use a before and after calibration to hone in on the perfect calibration cycles. 

Replaceable Sensors™

What Are Replaceable Sensors™?

A Replaceable Sensor™ is a removable part of your device that houses the chip which takes the actual temperature/humidity reading (or has an attached probe that takes the reading). By separating this from the device, it allows Dickson to offer a plug and play calibration solution.

WITHOUT REPLACEABLE SENSORS™

  • 1. Order a recalibration for your device
  • 2. Acquire a Return Authorization Code from a Dickson Representative
  • 3. Take unit out of its environment
  • 4. Move products out of environment/ install backup monitoring system
  • 5. Box unit up
  • 6. Ship unit to Dickson
  • 7. Dickson recalibrates unit and ships it back
  • 8. Receive the unit
  • 9. Disassemble backup system/move product back into environment
  • 10. Disassemble backup system/move product back into environment
Total down time: 7-10 days

VS.

WITH REPLACEABLE SENSORS™

  • 1. Order a Replaceable Sensor™
  • 2. Replace the old sensor without powering down or unplugging your device
Total down time: 0 days

Why Choose Dickson's Calibration Service?

Using Dickson's ISO 17025 A2LA accredited calibration laboratory is the best way to ensure that your Dickson instrument is calibrated properly. With over 90 years of experience, we have SOP's in place to ensure that each unit is calibrated to a precise and accurate specification.
Calibration Included Documentation Calibration/ Recalibration
Standard - -
N100 / N150 1-Point NIST Calibration and Certificate $99 / $156
N300 / N350 3-Point NIST Calibration and Certificate $156 / $209
N400 / N450 3-Point NIST & A2LA Calibration and Certification $269 / $315
N550 3-Point NIST Recalibration with Before Data and Certificate $269
N995 Custom Calibration Point $50

FAQ

Using Dickson's ISO 17025 A2LA accredited calibration laboratory is the best way to ensure that your Dickson instrument is calibrated properly. With over 90 years of experience, we have SOP's in place to ensure that each unit is calibrated to a precise and accurate specification. Why Should I Calibrate? You should calibrate because the accuracy of measurement devices drifts over time and you need to be certain that your device is accurately recording environmental values. When your temperature sensor is put under test, adjustments are made if inaccuracies are found. Changes are made to the sensor to align with the standard. These changes are called an adjustment. Who Says What is Accurate? So who says our standard is accurate? Who knows what 70°F feels like? Who says a yard is a yard? It may seem arbitrarily argumentative, but it’s a compelling question. The answer is NIST. Who is NIST? NIST stands for the National Institute of Standards and Technology. This government agency creates and maintains standards of measurement for length, mass, time, etc. In regards to temperature, standards are sent in by manufacturers, and those standards are calibrated to an even more accurate standard. They then become a NIST certified standard, which the Dickson calibration lab then uses to calibrate your device. What Does NIST Traceable Mean? At Dickson, we have temperature sensors calibrated by NIST that measure temperature with a NIST certified accuracy. Your temperature sensor is then compared and adjusted to these standards, to ensure its accuracy. This process is documented, and thus your calibration is traceable back to the NIST standards. You receive documentation with your device to back this up. What is a 1-Point Calibration? In its most simple form, a 1-point calibration means your unit will be calibrated at one specific point on the temperature scale. This is good if the temperature in your application varies by very little. An example: A calibration lab determines that a device is reading 26°F when it should actually be reading 24°F. So, the calibration lab adjusts the device two degrees, so that it now reads 24°F. A 1-point NIST assures accuracy at this specific point. Additionally, you may choose to specify this point to best reflect your application. What is a 3-Point Calibration? A 3-point NIST calibration differs from a 1-point NIST calibration in the amount of points checked for their accuracy by a calibration lab, and thus the document that is generated. The 3-point calibration consists of a high, middle, and low check, and thus grants you proof of accuracy over a larger range. Additionally, you may choose to specify these three points to best reflect your application. What is a Zero Adjustment? A zero adjustment is also called an offset. If your standard reads 26°F, but the device displays 24°F, your device is off by 2°F. You need to adjust the device two degrees in order for it to read accurately. A zero adjustment will shift the entire scale by 2°F even if the extreme ends of the scale were not off by 2°F. What is a Span Adjustment? A span adjustment is when you adjust the device on a curve. In the example above, we’d adjust the device by 2°F at 24°F, but the extremes wouldn’t need any adjustment and therefore would be relatively unaffected. When Does My Calibration Expire? Some factors to consider:
  • Environment: The more extreme the conditions (really hot or really cold) the more likely the device will drift over time. Dust, dirt, moisture, air particles can all contribute to a device needing to me recalibrated more often as well
  • SOPs: Your standard operating procedure (SOP) may require you to recalibrate more often than our recommendation
  • Regulations: Different industries are subject to different regulations and may require calibrations more or less often than our recommendation. It is best to check with your regulatory agency
  • Auditors: Some auditors have their own preferences on how often a device should be calibrate. Most often they adhere to the regulations for their industry/regulating body, but this isn’t always the case. Be sure to ask them what they’ll be expecting
  • Physical Damage: Dropping, kicking, bumping, or otherwise damaging your device may mean it will need to be recalibrated more often.
You can also use a before and after calibration to hone in on the perfect calibration cycles.