A calibration bath is an ideal temperature source for temperature calibration. Here are some of the things that you should consider or look for when choosing the right calibration bath for your company or factory:
Controllers
The first step in evaluating a bath is to look at its temperature controller. Fluke Calibration designed its own proprietary control technology to deliver stability to ±0.0001°C with features that make your work go more quickly. Their hybrid analog and microprocessor design are unique. Set-point resolution is 0.01°C (0.002°C on some models), and their “Super-Tweak” resolution mode shifts the controller display so you can adjust the bath set-point to the fifth decimal place. Although thermal noise in the bath is measured at four decimal places, the “Super-Tweak” function still gets you closer to an absolute temperature than any other controller. If you need a bath set at exactly 25.000°C, a Fluke Calibration bath gets you there with less effort than any other bath.
Eight of your most frequently used set-point temperatures are stored for quick recall and faster bath setup. Temperature can be easily switched between Celsius and Fahrenheit. Safety cutout temperatures are also set on the LED display.
Fluke Calibration baths are each fitted with a high-stability PRT or thermistor as the control sensor. Its controller uses special noise-rejection techniques to allow you to measure the very tiny resistance changes required for this level of bath stability. In this design, they use ac bridges to reduce thermal EMFs. Custom, high-precision, low-coefficient resistors contribute to short- and long-term stability of the temperature setting, and advanced filtering techniques force out line noise along with stray EMIs and RFIs.
A proportional, integrating control function directs power to the bath heaters. Factory tuning eliminates most overshoot and allows the bath to achieve maximum stability within 10 to 15 minutes after reaching the set temperature.
Automation
Another bath issue is automation and that is something that you should look out for. Fluke Calibration offers a number of options. You can select from an RS-232 interface or IEEE-488. The RS-232 packages come complete with Interface-it software so you can immediately start controlling your bath from a PC without any programming skills
Fluke Calibration’s entry-level benchtop bath series uses a simple on/off function to control refrigeration power. However, their higher performance baths use a heating/cooling equilibrium design that’s unique in the industry. A manual valve adjusts the cooling power to properly balance the refrigeration against the active control of the resistance heaters. Fluke Calibration’s bath interface packages include automated valves to make these adjustments automatically by your PC.
Heat Port Technology
A major factor in Fluke Calibration’s bath performance is the heat port technology. Some manufacturers place separate heating and cooling coils directly in the bath reservoir. In this scheme, heat enters and exits the bath at two different physical locations. Fluke Calibration improves bath uniformity and stability by reducing the heat paths from two to one.
Mixing
For mixing the bath fluid, Fluke Calibration uses a carefully balanced stirring mechanism. The number of propellers and the pitch of the blades are adjusted to thoroughly mix the bath medium and eliminate both horizontal and vertical gradients. They don’t use circulating pumps, because the tubular inlet and outlet design cause thermal-flow patterns in the bath that create unnecessary gradients. Our mixing scheme and the size and shape of our tanks all combine to deliver great performance.
They use two types of stainless steel tanks. Some of their smaller baths use deep-drawn tanks while the larger baths have tanks made of heavy-gauge stainless steel that is fabricated and welded in their own factory so they can control quality. Fluke Calibration baths have larger well openings than other baths. This makes them an excellent choice for sensor manufacturers and others that test large batches of sensors or special probes of unusual size and shape.
Maintenance
Fluke Calibration baths are easy to maintain because their stir motors last longer; there are no pumps to unclog or repair. Their bath tanks are easier to clean because they don’t have heating and cooling coils in them. (Source: Fluke Calibration)
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