• Step 1. Know why, how, and where you will gather environmental data
• Step 2. Prepare your PEMs and start gathering data
• Step 3. Control the urge to check data too often
• Step 4. Transfer data from the PEM with an SRAM card

Step 2. Prepare your PEMs and start gathering data

Either start up a new PEM . . .

• Prepare the PEM just prior to placement. To begin, the PEM should display OFF at the top and three dashes at the bottom.
• Press and hold the recessed PAUSE button with a pencil point or paper clip until the display flashes 1-2-3. Release on 3.
• The PEM is now in Normal Operation mode, gathering and storing data. The display should alternate between TWPI/PI and TEMPERATURE/HUMIDITY every fifteen seconds. (The TWPI will be incorrect for the first 30 minutes.) If you are still seeing PAUSE, press and release the recessed PAUSE button again.
• Once the PEM is operating normally, you can turn the display off or on by pressing and holding the F/C button for three seconds.

. . . or clear an existing PEM of all data and restart it in a new location

• Be sure you have saved the existing data on your computer, because this step will wipe it out! The PEM operating parameters and real-time clock will remain.
• Press and hold all three buttons (READ, F/C, and recessed PAUSE) simultaneously for three seconds. The screen will display CLR/RESET/ALL, and will then return to OFF.
• To begin collecting data, proceed as described above for a new PEM.

What the PEM is doing

• Data is being stored in two different memory banks called “buffers.”
• One buffer holds temperature and RH readings made every 30 minutes and will hold about one year’s worth of data.
• The other buffer holds temperature and RH readings made every 4 hours, and will hold about five years’ worth of data.
• When a buffer fills up, new data overwrites the oldest readings.
• Both buffers are copied to the card during upload. Users choose which data they want when saving it to the computer.
• The PEM is calculating and displaying the preservation index (PI) based on ambient temperature and RH. The PI expresses in units of years how long it would take for vulnerable organic material to become noticeably deteriorated assuming that the temperature and RH remain the same.
• It is also calculating and displaying the time-weighted preservation index (TWPI), which adds the element of time and the cumulative effect of deterioration to the PI to give a more realistic estimate of the long-term effect of environment on preservation.