McDry Ultra-Low Humidity Storage Cabinets: Humidity Control



The digital hygrometer ERC-301B is used to monitor humidity levels within McDRY.


  • Static capacitance type sensor
  • Measuring range: 1-70% RH
  • Accuracy: ±3% RH
  • 4 AA Alkali batteries; approx. 1-year service life


Batteries are utilized so that in the event of power supply interruption or when the cabinet is unplugged for relocation, the meter may continue to display the humidity level within the cabinet

Hygrometer Calibration

IC packages should be stored in a dry box (McDRY) at < 5% RH in conformance with the IPC-JEDEC specification for prevention of moisture absorption and indefinite safe storage of MSDs. However, correct humidity control is impossible unless the hygrometer reading is reliable. Be sure to calibrate the hygrometer at least once a year.

Hygrometer With Alarm

By setting the RH limit with the ERC-301AD hygrometer, an alarm light will flash when the humidity level becomes too high.

  1. The alarm light will flash when the humidity level goes over the set limit after a fixed period of time.
  2. After the alarm light flashes, the unit will save 100 data readings, one per hour.
  3. When the humidity level goes over the set limit, the (optional) light tower will flash and a buzzer will sound.


Example: Humidity data after the alarm light flashes (1 reading per hour)

Time (h) Humidity(% RH
0 30
1 30
2 30
3 40
4 40
5 40
6 40
7 40
8 40
9 40