A chamber is chosen from the test condition backwards. Engineers who order from a model list usually buy either too much machine or one that cannot hold the duty. Seven inputs decide the configuration.
1. Temperature range — set the extremes first
Standard temperature-humidity chambers (ETH series) cover −70 °C to +180 °C. Rapid temperature change chambers run −70 °C to +180 °C. Thermal shock chambers are ordered by low-end class — −40 W, −55 W, −65 W — with an optional −70 °C to +200 °C configuration. If the upper limit you actually use is +85 °C and the specimen is large, a walk-in chamber may be the better choice; above +85 °C the construction has to change. Match the range to the standard, not to the widest catalogue value.
2. Ramp rate — an average no-load figure is not a loaded figure
Published rates are average, no-load values. The rapid temperature change series is offered in 5, 10 and 15 °C/min steps, and up to 30 °C/min is achievable. Rate is not free: rated output on a 1,000 L rapid-change chamber reaches 38–65 kW. Decide the rate the product must see, then check it against specimen mass and heat load.
3. Working volume — leave a path for the air
We build chambers from 100 L to 12,000 L. Cabinet models in the ETH, ETS and EQT families start at 23–125 L and step through 225, 408, 800, 1,000, 2,160 and 8,900 L; walk-in chambers cover 7.8–44.1 m³. A specimen that blocks the airflow path spoils uniformity whatever the rated volume is. Size for the fixture and the clearance around it, not for the bare device.
4. Specimen heat load — subtract it from the cooling budget
A powered specimen adds heat that the refrigeration system has to remove. State the load in watts at the test temperature. A chamber that reaches −70 °C empty may not hold −70 °C with a 2 kW load. Heat load affects both the achievable low temperature and the attainable ramp rate.
5. Humidity — fit it only if the test needs it
Humidity models cover 10% to 98% RH with ±1.0% RH uniformity; relative humidity deviation is ≤ ±3.0% RH above 75% RH and ≤ ±5.0% RH at or below. Humidity adds a water supply, a demineraliser and a drain. A temperature-only test does not need it.
6. Uniformity, fluctuation and deviation — three separate numbers
Temperature fluctuation ≤ ±0.5 °C, temperature deviation ≤ ±2.0 °C and temperature uniformity ≤ 2.0 °C are different specifications. A test method written around a tolerance depends on which one the chamber is specified to hold.
7. Site conditions
A chamber needs a controlled laboratory ambient, a floor drain for condensate and the right supply — 380 V, three-phase, four or five wire. Water-cooled models need cooling water at the stated flow. Confirm the site before placing the order.
Turning the answers into a specification
List the seven inputs and we can return a configuration: the standard you are testing to, specimen size and heat load, required temperature range, required ramp rate, whether humidity is needed, and the site data. Contact us with those and we will map them to a chamber and control arrangement.