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Section 1
GENERAL INFORMATION
1.1 GENERAL DESCRIPTION
The Thunder Scientific Model 5A-1MP is a microprocessor based Laboratory Standard
Psychrometer designed for precise measurement of air temperature and relative humidity.
The 5A-1MP uses a 2-bulb measurement system employing Wet and Dry calibrated
Platinum Resistance Thermometers (PRT's) operating under a controlled air velocity. One
PRT, referred to as the Dry Bulb, is used for sensing air temperature. The other PRT, the
Wet Bulb, uses a specially woven wick (or sock) to facilitate an unimpeded capillary flow of
distilled or high purity reagent water from a reservoir below. The Wet Bulb measures a
depression temperature.
The signals from the PRT's are converted to digital format, read by the microprocessor, and
mathematically corrected to temperature data. The data is then used to calculate Percent
Relative Humidity and Dewpoint Temperature.
Front panel display of any of the above data is selected by user input at the keyboard. The
upper display is the data readout device, and the lower display indicates which data or other
function is currently enabled. Upon selection of data output to this real-time LED display,
current readings are updated four to five times each second allowing for fast system
response to any changes in the sampled environment.
Printer output, enabled from the keyboard, allows for hardcopy printouts of all current
psychrometric data. Printer output is at user selected time intervals ranging from a one
minute minimum to 24 hour maximum, or at any one minute increment in between.
An Auto Mode feature is also included which, when enabled, will put the probe in
synchronous operation with the printer. In this mode, the probe aspirator will automatically
run prior to any sample for hardcopy output. After printout, the aspirator will be disabled
and will remain off until the next sample time is reached.
Bi-directional RS-232 and optional IEEE 488 communication capabilities allow for remote
operation and data retrieval when connected to a computer or terminal. All functions
available from the front panel keypad are also available over the RS-232 and IEEE 488 links
through a series of more than 40 commands.
The Model 5A-1MP is a precision laboratory grade instrument, and when operated and
handled accordingly, will provide years of excellent service.
