DAVIS Health EnviroMonitor User Manual download pdf (Page 45)

Health EnviroMonitor Overview

Page 6 Health EnviroMonitor Manual

EATHER

ONDITIONS

EASURED

ALCULATED

This section outlines each of the weather conditions measured/calculated by

the Health EM. Each section includes a brief discussion of the weather condi-

tion and a listing of the various ways in which the unit displays or stores that

condition. Be aware that some of the weather conditions require an optional

sensor in order to measure/calculate a value (see “Optional Sensors” on

page 1). If you do not have the required sensor that reading will appear as a

series of dashes in the Health EM display.

Values which are described as “Daily” readings will provide true daily read-

ings only if they are cleared each day. You may clear these values yourself or

use AutoClear (see “AutoClear” on page 11) to clear them for you. If you do

not clear the values every day, then you can use the “daily” readings to repre-

sent any interval you desire: two days, one week, one month, etc.

The notation “(AutoClear)” next to a weather condition indicates that the

Health EM’s AutoClear function may clear the weather condition at a set time

every day. For information on AutoClear, see “AutoClear” on page 11.

The notation “(Alarm:)” next to a weather condition indicates that an alarm

exists for the weather condition. The type of alarms are noted after the colon.

For information on Alarms, see “Alarms” on page 12.

Heat Stress (Temperature-Humidity Index)

Temperature-humidity index (T-H index), commonly called heat stress, uses

the temperature and the relative humidity to determine how hot the air actu-

ally “feels.” When humidity is low, the apparent temperature will be cooler

than the air temperature since perspiration can rapidly evaporate into the air.

However, when humidity is high (i.e., the air is saturated with water vapor) the

apparent temperature will be higher than the air temperature.

If you have an anemometer and solar radiation sensor, the Health EM takes

into account the effects of sun and wind in determining how hot the air actu-

ally “feels.” This reading is called the Temperature-Humidity-Sun-Wind index

(T-H-S-W index). If you have only an anemometer or only a solar radiation

sensor, the Health EM will still report the T-H-S-W index, taking into account

whatever factors are available. In addition, the display only shows those seg-

ments for which you have a sensor. For example, if you only have a temp/hum

sensor and an anemometer, the Health EM will calculate the T-H-W index (tak-

ing into account only the effects of temperature, humidity, and wind) and only

display the TEMPERATURE, HUMIDITY, and WIND segments. Unfortu-

nately, the absence of either the anemometer or the solar radiation sensor can

lead to inaccurate readings, especially when the wind or solar radiation read-

ings are high.

Note:

The Health EM measures T-H index (and T-H-S-W index) only when temperature is above 68˚ F

(20˚C) because it is a measure of heat stress which is not signiﬁcant at lower temperatures. 125˚ F

(52˚ C) is the highest T-H index for which calculation factors are available. Above 125˚ F (52˚ C),

the system simply reports that T-H index is “high.”

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DAVIS Health EnviroMonitor User Manual Page 45

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