Enclosure & Autoclave Validations with the Fluke 1586A Super DAQ Temp Scanner

Here at CPS we often get the call to test temperature controlled enclosures. It’s a common requirement that testing laboratories can prove their enclosures, such as incubators, ovens, chillers, and freezers, maintain a certain degree of uniformity and stability. Likewise, with Autoclave sterilisers, it’s important to validate that the loads being sterilised and achieving the temperature and time required for adequate sterilisation.

To test and validate these temperature controlled enclosures and autoclaves you need to be able to measure and record the temperatures at different locations within the enclosure simultaneously. To do this accurately requires somewhat sophisticated and expensive data acquisition (DAQ) equipment and knowledge of how to use it properly. Traditionally this has been done with some DAQ hardware communicating to software on a computer which records the readings. The problem with this type setup is that with several pieces of equipment it creates several areas where things can go wrong. Common problems I’ve experienced with this is having the comms dropping out between the DAQ hardware and my computer. Or my laptop batteries dying because someone has switched off the power at night while running a test. You come back the next day to find your 4 hour test has only recorded 30 mins of data!! Not to mention the time to set it all up and pack it all down.

The Fluke 1586A “Super DAQ” Temp Scanner removes all these potential problems and makes the job a lot easier and more accurate in a relatively inexpensive package. It’s an all-in-one device which requires no setup on-site, just turn on and start recording.

One of the main considerations when putting together your testing system is the choice of temperature sensors to use. Thermistor, RTD, or Thermocouple (TC). Thermistor & RTD sensors provide the greatest accuracy and lifespan, however they are a lot more expensive and have other drawbacks. This includes a much larger lead diameter which makes it more difficult when trying to get a good seal through an incubator door or a small autoclave penetration.
For these reasons the sensor most commonly used for enclosure testing is TC wire probes. They are relatively cheap and easy to construct to custom lengths. They do however have one main drawback and that is that for them to remain accurate the wire must be homogeneous which means the wire must remain uniform in structure or composition throughout. Inhomogeneities can occur in the wire from mechanical damage due to bending and twisting, changes in the wire diameter, and chemical changes due to oxidation. Any inhomogeneities where there is a temperature gradient will result in measurement errors. That is a very real problem for us testing enclosures as the place where there is the greatest temperature gradient is also the place where we are most likely to bend, kink, or crush the TC wire – the enclosure door or chamber penetration. To get around this problem it therefore becomes best practice to calibrate the TC probes “in-situ” against a known reference. The enclosure testing procedures we’ve introduced at CPS follow this method. We place a calibrated RTD reference probe inside the enclosure and calibrate our TC probes against this all grouped together inside the enclosure at the applicable temperature.

The Fluke 1586A has two main features which I really like and make this unit stand out:

1. You can configure any single input to take any sensor. So you can setup channel 1 to be and RTD input while at the same time make all the other inputs TC inputs. Most other DAQ hardware doesn’t give you this ability, you’re usually stuck with either all TC inputs or all RTD’s etc… This means you don’t need a another piece of equipment to act as the reference.

2. The in-situ calibration becomes very simple as the Fluke 1586A has a feature which allows you to align all the channels at the press of a button. You simply select which channel is your reference, then at the press of a button, all the other channels will be aligned by adding offsets to match your reference.

Once the recording parameters have been configured the recording process is a very simple press of the button to start and stop. It can also be configured to stop at a certain time or after a set number of samples as well as many other configurable parameters such as sample frequency. At the end of a test the data is simply downloaded onto a USB flash drive for you to take away.

Since we’ve began using the 1586A I’ve found it saves time and gives me a far greater degree of confidence in my results. I know I can setup and start a test and leave it to run without the constant monitoring that other systems often require. It makes the job far easier and gives me piece of mind which makes the 1586A an invaluable asset.

There are many other features and options that make the Fluke 1586A a great product to use including the ability to communicate with Fluke calibration baths to automate calibrations. You can lookup and find more information from the Flukecal website here:

http://us.flukecal.com/products/temperature-calibration/digital-thermometer-readouts/1586a-super-daq-precision-temperature-

Paul Martin Laboratory Manager CPS (NZ) Ltd – New Plymouth, NZ