It is possible to have widely different readings between your portable data loggers and your building sensors. How to know when something really is wrong.
Sensors of any brand will have a +/- accuracy range within which they can be considered correct. Variations in these ranges added to time in between calibration services as well as types of sensors will affect these.
While Conserv sensors are not perfect and can sometimes have calibration issues, more often than not, their readings are very accurate. This does not mean that we are not willing to replace sensors that are not working properly. At Conserv, we are committed to providing you with good quality equipment that is accurate and helps you protect your collections.
However, we do not recalibrate your faulty sensors. We just replace your sensors for new ones. This means that if you need your sensors "fixed", we just ask you to send them back and send you new ones instead. This involves a cost related to both shipping and carbon footprint, so we like to be absolutely sure that your sensors really need to be replaced before we start this process.
Compare apples to apples
Whatever sensors you will be comparing, you will need to make sure you are comparing apples to apples. Here is a little checklist of things you need to make sure are not acting as independent variables during your comparisons.
-
Are they reading from the same location?
Microclimates are real. If you are comparing any data logger in a space with a sensor in your HVAC system, you should not expect readings to be the same. For a true comparison, both sensors need to be placed next to each other in the same space. -
What is the standard of error for each?
Every sensor will have the standard of error in its specifications. For example, in the example in the image above, the Conserv sensor on the left has a standard of error of +-2% RH and +-0.2°C. So if the real conditions of a space are 50% and 20°C, any reading by the Conserv sensor that says 48-52% and 18-22°C can be considered correct. -
What is the annual drift for each AND when were they last calibrated?
Apart from standard of error, equipment also comes with an indication of annual drift, which is the amount of accuracy that a sensor loses each year due to regular wear and tear. If you look at the image above, Conserv (version 1) sensors have an annual drift of +-0.25% per year, which is why we replace them every 3 years. At the end of the 3 years, you will be having to add a +-0.75% to your RH reading on top of the standard of error. Annual drift can be said to be "reset" on the date a sensor is calibrated.
Important note: Calibration date is particularly important when comparing standalone data loggers to building facilities sensors because it is not uncommon for building sensors to not be calibrated at all, with some facilities staff preferring to account for the drift in the calculations rather than getting the equipment adjusted. Please make sure you communicate with your facilities and operations staff so you can be sure you are comparing apples to apples.
Why is all this math important?
Once you add up the standard of error, annual drift and calibration dates for each equipment, you will notice that it is possible to have a range of even 6%RH and still have two devices that are considered to both be correct.
In the example we have been using in this article, you can see a maximum allowable difference in readings of up to 5.25%.
Circling back to shipping and carbon footprint
Are Conserv dataloggers perfect and 100% free from fault?
No, any sensor from any brand may have hardware related issues. In Conserv's case, because we run on a subscription model, we will stand behind the equipment throughout your subscription period.
Will Conserv replace a sensor that is malfunctioning and out of its expected calibration numbers?
Certainly!
Will we ship sensors back and forth without concern for the environmental cost?
Ideally not. If you find that your Conserv equipment is not reporting numbers identical to your facilities or building sensors, this is normal. Please make sure we are comparing apples to apples before we initiate replacement procedures.
More resources to help you
We have written a number of articles that can help you get more information on this topic and get the specs you need for your calculations: