ACR Electronics SmartReader Plus Manual de usuario descargar pdf (Pagina 80)

SmartReader Data Loggers

2. MgCl2 x 6H2O, 150gm (Fisher #M-33)

3. NaCl, 50gm (Fisher #S-271)

· De-ionized or distilled water, 75ml for each solution

Prepare for the saturated salt test by following these steps:

1. Use the powder funnel to carefully place the salt into the center of the jar bottom.

2. Slowly pour the water onto the mound of salt, using the long stem funnel, taking care not

to splash any water or salt onto the inner walls of the jar.

3. Gently swirl the saturated solution. If the salt dissolves entirely, with no crystals

remaining on the bottom, the solution is not saturated and more salt must be added.

There must be crystals remaining on the bottom but they must not be exposed above the

water level.

4. Put a nail through the jar lid and bend into a small hook. Tape the head of the nail (or

use rubber cement) to create an airtight seal of the opening. The logger with RH sensor

(or EH-020A) can be inserted into the jar by first hanging it on the nail loop then screwing

on the lid to the jar.

5. The saturated salt solutions should be kept in a well insulated environment to minimize

any temperature changes. The equilibrium RH over saturated salt solutions is only

slightly temperature dependent. However, for close calibration work to 5% RH or better, it

is important to keep the temperature of the salt solution and the air space above it

identical. To ensure this, the temperature of the lab should be constant.

To perform the saturated salt test, follow these steps:

1. Setup your relative humidity logger with a sample rate of 20 seconds and equation 38 on

the RH channel(s). Make sure you have selected Normalized Byte data units.

2. Place the jars into the box with 1 to 2 inches of Styrofoam chips on the bottom, then fill all

remaining air spaces between the jars and the interior spaces of the box with the chips.

3. Cover the box with cardboard in which 6cm (2.5") diameter holes have been cut to allow

access to the tops of the jars for insertion of the logger or RH module.

4. Place the logger with sensor or EH-020A module into the jar containing the LiCl solution

(RH = 11%) overnight to eliminate any hysteresis effects.

5. Quickly insert the logger (or module) into the next solution by swapping the lids.

Transfers should always be made in the direction of higher RH conditions. The jar

should be well sealed. Allow at least two hours to get within three percent of the

equilibrium RH. Repeat for next solution.

Salt

MgCl2

33%

NaCl

75%

6. Call up the graph on your computer using TrendReader software. The profile you see

should reflect the test you have just performed.

7. Zoom in on the section that relates to the 33% RH level in the test chamber. Use the

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ACR Electronics SmartReader Plus Manual de usuario Pagina 80