Please select a category or scroll through the entire list:
Operating the PEM
Understand the PEM Display
SRAM Cards
Collecting Your Data
Recalibrating Your PEM
Why should I buy a PEM for $650 when I can buy a datalogger for $150?
Because they don't do the same job. There are many types and styles of dataloggers available that offer varying degrees of: accuracy, support, software and specialization to a particular task. The PEM is specifically designed to do two things very well:
- It gathers temperature and humidity data accurately and efficiently for institutional preservation programs. A datalogger that suits the needs of preservation monitoring is one that makes the task easiest, most reliable and continuous. Experienced datalogger users know that the time spent configuring loggers and collecting and organizing data is the biggest expense in monitoring, not the original price of the logger itself. The PEM's card upload extracts the data in 20 seconds and its five-year data capacity forgives inattention and ensures that no data is lost.
- The PEM provides a direct, real-time display of TWPI (Time-Weighted Preservation Index), a measure of how fast organic materials are decaying due to "natural aging." This number is a scientifically grounded measurement of the quality of the storage environment from the preservation viewpoint. It is the basis for both better collection care decisions and an opportunity to educate staff, facilities and managers on the importance of good environmental conditions. Having the TWPI on display in the storage area is a powerful managerial and educational tool for preservation professionals.
Yes. Although it is hard to do, there is one way to lose your data:
There isn't one. The PEM is designed to have power on at all times. Unless the "display off" mode has been selected (intended for use in galleries or public display areas) there should always be something visible on the display.
The display says "OFF." How do I turn it on?
First locate the circular recessed button located on the left side panel of the PEM - between the "READ" and "F/C" buttons. Next, press and hold the recessed button for 3 seconds using the point of a pencil or an unbent paper clip.
The "Pause" mode prevents the temperature and humidity data from being entered into the PEM's memory. There are two reasons for using this mode:
- Relocation of the PEM: Let's say your PEM is kept in an office for some days between placement in collection storage areas then the data collected in the office may be of no interest. By putting the PEM into "Pause" mode, you have ensured that the office data is not stored in the PEM.
- Reinitializing the TWPI (a special kind of running average of the Preservation Index): If the PEM is moved to another location you wouldn't want the data from the old location to influence the analysis of the new location. In order to begin the TWPI calculation again in the new location you simply put the PEM into "Pause" mode.
When the PEM is in "Pause" mode temperature and humidity readings are still taken but they are not saved into memory. Additionally, only PI values will be displayed in "Pause" mode - TWPI will not be calculated or displayed.
How long do the batteries last?
Between five and ten years. This varies depending on how many uploads you do and how often the "History" mode is used but most users should not need replacement batteries for 6-8 years.
What kind of batteries does the PEM use and how do I replace them?
The PEM uses a 9 volt lithium or alkaline batteries. We recommend Lithium 9 volt batteries because they last longer than alkaline batteries. Lithium batteries are sold in large home centers and hardware stores for use in smoke detectors. Three lithium batteries are usually sufficient although up to 5 may be installed.
To replace the PEM batteries, place the unit face down on a clean flat surface. Remove the four screws holding the back of the case - this requires a small Phillips head screwdriver. Next, remove the back cover. Replace the batteries, taking care to observe the correct polarity (that the batteries are facing the right direction!). snap the new batteries snugly into place - they should not be loose or rattle. Finally, replace the back cover and screws.
Don't WORRY! The PEM will continue to run normally during the battery replacement.
The "Ship" mode is a sleep mode used for shipping. In this mode the PEM doesn't take readings or store data. Battery life is thus saved and drains on the batteries - caused by the inadvertent depression of buttons - are prevented.
Is the PEM always collecting data?
No. Although the PEM is always powered up to keep time and store data in the internal RAM is one mode that does not collect data - "Ship" mode.
What are the different types of PEM modes?
The PEM has three basic modes:
- SHIP Mode: the display reads "OFF". NO readings are mad and NO data is stored.
- PAUSE mode: The display shows T, RH, and PI. The word "Pause" appears in the display. The PEM continues to take readings and display them every five minutes but NO data is saved. In this mode the PEM acts like an electronic thermometer but not a datalogger.
- NORMAL mode: The display shows T, RH, PI and TWPI. Readings are made and data is stored.
Note that the PEM stores data for upload into a computer ONLY in the "Normal" operating mode. Be sure to verify that your PEM is in "Normal" operating mode by checking that the temperature and RH values appear in the display AND that the word "PAUSE" does not appear.
Mode
Display
Measures T and RH?
Saves data?
There's nothing showing on the display. What's wrong?
This usually means that the PEM has the display turned off. Readings are still taken and saved but the display remains blank. This option is intended for galleries and other situations where the PEM display would be distracting.
What does the indicator "Batt Low" on the display mean?
It's time for new batteries. When the combined voltage on the main batteries has dropped to a point where fresh batteries are recommended, this warning displays. There is an internal backup battery so there is no danger of losing any data during the replacement of the main batteries. The backup battery will power the PEM for a year or more after the "Batt Low" warning appears.
The temperature reading seems strange. It's only a fraction of what it should be or it's way too high. What's wrong?
The PEM is probably displaying the temperature in degrees Celsius rather than Fahrenheit or vice-versa. You will find "F" or "C" in the upper right hand corner of the display.
These are credit-card sized memory cards that are used to transport the data from a PEM to a computer - you can think of them as behaving something like a floppy disk. SRAM (Static Random-Access Memory) cards contain memory chips and a tiny lithium battery. They come in several sizes, the most popular being the 1 and 2 MB cards. The 1 MB card can hold the data from 8 PEM's while the 2MB card can hold the data from 16 PEMs.
What are the SRAM cards used for in the PEM?
The SRAM card is a handy way to transport the data from a PEM to a computer - you can think of it as a special kind of floppy disk. The PEM stores recorded data in its own memory buffers it copies its data onto the SRAM card. The data is still stored in the PEM after it has been copied onto the card.
What about all these SRAM card aliases like "PC Card" or "PCMCIA Cards"?
The SRAM cards used but the PEM are part of an electronics industry standard known as the "PC Card" or "PCMCIA Card" standard. The standard, created in the 1990's, defines the way to connect modems, network cards, memory cards and other devices to portable computers. It specifies certain features:
- the size (about the size of a credit card
- the pin assignments (PC Cards have 68 tiny pins in the connector)
- the electrical signal paths
Nearly every Windows laptop computer has one or more PC card slots. Desktop computers do not typically have PC card slots - you have to buy an add-on card reader. These are available in either internal designs (fitted inside your PC like a floppy disk drive) or as an external design that plugs into your printer port.
What is that tiny little switch on the SRAM card for?
That is the card's write protect switch similar to those found on floppy disks. No data can be copied to the card if this switch is set to "write protect". If the write protect switch has been accidentally set you will see "Crd Pro" on the PEM display when you try to copy your data to the SRAM card. This is PEM's way of warning you that it cannot upload the data to a write protected card.
Does the SRAM card have a battery?
Yes. There is a small lithium coin cell in the SRAM card. The purpose of this battery is to keep the data alive in the card's memory. When the battery dies, all the data in the card is lost. There are some SRAM cards that actually have two batteries, one very small one to keep the data while changing the main batteries. The life of the battery in the SRAM card depends on its memory capacity. The batteries in 1MB SRAM cards usually last three years or more. The batteries in a 2MB are typically good for about two years.
How much data does the PEM hold?
Unlike other dataloggers, the PEM actually has two blocks of memory to store it's data, that is, it has two buffers:
- 30-minute buffer: contains the data collected at 30 minute intervals.
- 4-hour buffer: contains the data collected at 4 hour intervals.
The 30-minute buffer will hold about one year's worth its data (taken at 30 minute intervals). The 4-hour buffer will hold about five years' worth of data taken at 4 hour intervals.
When you copy data from the PEM onto the SRAM card, you automatically copy the contents of both the 30-minute and 4-hour data buffers into one file. Each buffer is approximately 64KB in size, so combined they total roughly 128KB.
Later on, when you are working with PEM data or Climate Notebook software to view the data, you will have to choose which data buffer you want to work with. The 30-minute buffer will give more detail but, as time goes on, a lot of data will be accumulated. After a year, the 30-minute buffer will contain 17,530 data points (the number of half-hours in a year). so, although you will get much more detail, it will take much longer to process these files. In most cases, using the four-hour data buffer for longer time spans gives enough precision. One year's worth of the 4-hour data buffer will have 2,191 data points and will process much more quickly.
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Buffer Type
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Buffer Size
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Data Points per Year
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Pros
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Cons
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30-minute
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64KB
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17,530
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Greater Detail
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Slow to process for longer time spans
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4-hour
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64KB
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2,191
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Faster for longer time spans
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Less detail
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Why are there two data buffers?
It's the long-term averages of temperature and RH that are important for many types of damage to collections. Of course, some forms of damage can happen quickly but a continuous, long-term record of conditions is necessary in order to have a rational analysis of the effects of the environment on collection objects. One of the data buffers can hold 5 years' worth of data giving a convenient and relatively foolproof means of obtaining a long-term analysis of storage conditions, a key consideration in preservation.
Are the data points (temperature and RH) recorded every 30 minutes or 4 hours by the PEM instantaneous readings?
No, they are actually averages of temperature and RH readings made every 5 minutes. So, Each data point in the 30-minute buffer is the average of 6 readings made at five-minute intervals. The 4-hour buffer is made up of the average of 48 readings made at five-minute intervals. Therefore temperature and RH events that last only a short time will affect the average readings and have some impact, although their maximum extent will not be known.
If the PEM display is set to Celsius, will the uploaded data only be in Celsius on the computer?
No. Once in the computer, the data may be viewed in either Fahrenheit or Celsius as desired, regardless of what temperature scale is displayed on the PEM.
How do I get my Data out of my PEM?
The best way is to use an SRAM card, which plugs into the slot on the right side of the PEM (as you face the display). Slide the card into the slot, paying attention to the arrow indicating the proper direction. The card will only go in one way. Firmly seat the card (a little force is necessary, until it clicks into place). Momentarily press the READ and f/C buttons. The display will say "Crd" and "Uploading." Uploading will take about 20 seconds.
I am using a laptop computer. Now that I have uploaded my data onto the SRAM card from the PEM, how do I get it into my computer for analysis?
Laptops of all makes that use the Windows operating system typically already have PC card "slots" built into them (look on the sides of the laptop). However, Windows still needs to be told how to handle SRAM cards because SRAM support is not automatic (except in Windows 2000). Each version of Windows (95, 98, Me, NT and 2000) has a slightly different way of setting up SRAM card support. Consult the PEM user manual for details. When the setup is completed, each PC card slot appears to Windows as a disk drive. It will have its own Drive Letter (usually D: or E: ) and the files on the SRAM card will be visible by clicking on the Drive Letter in My Computer or in Windows Explorer.
I am using a desktop computer that has no built-in PC card slots. Now that I have uploaded my data onto the SRAM card from the PEM, how do I get it into my computer for analysis?
Purchase and external card reader that plugs into your computer's parallel printer port. This device has a small card reader attached. It will allow you to view the SRAM card as a disk drive in Windows (typically as drive D: or E: ). The files on the SRAM card will be visible by clicking on the Drive Letter in My Computer or in Windows Explorer. The external card reader device must be able to handle SRAM cards. Most such devices do not; they are designed for flash memory cards for digital cameras. The Adtron Accent LPC is the card reader that IPI recommends for use with the PEM. It is available form IPI. The exact installation procedure for the Adtron Accent will vary according to which version of Windows you are using.
What happens when the 30-minute data buffer is full?
The newest data overwrites the oldest, so there is always data from the present time back to approximately one year ago. A similar thing happens with the 4-hour data. After five years the newest data begins to overwrite the oldest.