A. Product Overview

The R-Tek RT-078 Sling Psychrometer is a portable instrument used for measuring wet bulb and dry bulb temperatures so that the relative humidity of the surrounding air can be determined.

R-Tek offers the RT-078 in two versions:

RT-078 Alcohol Filled

• Model: RT-078
• Product Type: Sling Psychrometer
• Scale Type: Centigrade and Fahrenheit
• Temperature Range: 0°C to 50°C
• Indicating Fluid: Red Alcohol
• Easy-to-read construction
• Designed to quickly and accurately measure humidity levels

RT-078 Mercury Filled

• Model: RT-078
• Product Type: Sling Psychrometer
• Scale Type: Centigrade and Fahrenheit
• Temperature Range: 0°C to 50°C
• Indicating Fluid: Mercury
• Easy-to-read construction
• Designed to quickly and accurately measure humidity levels

R-Tek states that its sling psychrometers are manufactured to a standard design using quality materials and are intended to provide accurate results.

B. Working Principle

The RT-078 Sling Psychrometer works on the wet bulb and dry bulb psychrometric principle.

A conventional sling psychrometer uses two thermometers:

1. A dry bulb thermometer measures the normal ambient air temperature.
2. A wet bulb thermometer has its sensing bulb covered with a moistened wick.

The psychrometer is moved rapidly through the air by swinging or slinging it. Airflow across the wet wick causes water to evaporate. This evaporation removes heat and lowers the temperature indicated by the wet bulb thermometer.

The temperature difference between the dry bulb and wet bulb readings is known as the wet bulb depression.

The relationship is straightforward:

• Dry air produces faster evaporation and a larger temperature difference.
• Humid air produces slower evaporation and a smaller temperature difference.
• At very high relative humidity, the wet bulb and dry bulb temperatures become closer.

The two readings can then be used with a psychrometric table or calculation to determine relative humidity. The National Weather Service describes this same principle for conventional psychrometers.

The R-Tek webpage does not specify the exact wick material, recommended slinging time, psychrometric chart supplied, or calculation method for this particular RT-078 model.

C. Why Is a Sling Psychrometer Used?

A sling psychrometer is used to determine atmospheric humidity using wet bulb and dry bulb temperature measurements.

Humidity is an important environmental parameter because it affects manufacturing processes, storage conditions, HVAC performance, laboratories, agricultural environments, material quality and human comfort.

Unlike many electronic humidity meters, a traditional sling psychrometer determines humidity through the physical process of evaporative cooling.

The RT-078 can therefore be useful when users require:

• Relative humidity measurement
• Wet bulb temperature measurement
• Dry bulb temperature measurement
• Ambient air temperature measurement
• Portable humidity checking
• Manual verification of humidity conditions
• Laboratory environmental measurements
• HVAC inspection and testing
• Warehouse environmental checks
• Storage area monitoring
• Industrial environmental monitoring
• Educational demonstration of psychrometric principles
• Meteorological observations

These are common applications of sling psychrometers based on their measurement principle. The R-Tek webpage itself states that the RT-078 is designed to quickly and accurately measure humidity levels but does not provide an application-specific list.

D. Suitable Buyers

The R-Tek RT-078 Sling Psychrometer can be useful for professionals, businesses and institutions that need portable temperature and humidity measurement.

Suitable buyers can include:

• HVAC technicians
• HVAC contractors
• Air conditioning service companies
• Laboratories
• Research institutes
• Schools and colleges
• Universities
• Meteorological departments
• Weather monitoring professionals
• Factories
• Manufacturing companies
• Quality control departments
• Maintenance departments
• Warehouses
• Storage facilities
• Agricultural facilities
• Facility management companies
• Industrial instrumentation suppliers
• Scientific equipment suppliers
• Laboratory equipment dealers
• Temperature and humidity instrument dealers

For regulated applications requiring a specific accuracy class, traceable calibration, NABL calibration or a particular certification, those requirements should be separately confirmed because they are not stated on the RT-078 webpage.

Frequently Asked Questions

1. What is the R-Tek RT-078 Sling Psychrometer?

The R-Tek RT-078 is a sling psychrometer designed for measuring humidity using wet bulb and dry bulb temperature readings. R-Tek offers it in alcohol-filled and mercury-filled versions.

2. What is the temperature range of the RT-078?

The specified temperature range of the R-Tek RT-078 Sling Psychrometer is 0°C to 50°C.

3. Does the R-Tek RT-078 measure relative humidity?

The RT-078 is designed for humidity measurement. A sling psychrometer determines relative humidity using the difference between wet bulb and dry bulb temperatures.

4. How does the RT-078 Sling Psychrometer work?

A wet bulb and a dry bulb thermometer are exposed to airflow while the instrument is swung. Evaporation cools the wet bulb. The difference between wet bulb and dry bulb temperatures can then be used to determine relative humidity.

5. What is wet bulb temperature?

Wet bulb temperature is the temperature indicated by a thermometer whose sensing bulb is kept wet and exposed to airflow. Evaporation causes cooling, so its reading is generally lower than the dry bulb temperature.

6. What is dry bulb temperature?

Dry bulb temperature is the normal ambient air temperature measured without a wetted sensing bulb. It serves as one of the two measurements required for psychrometric humidity determination.

7. Why are two thermometers used in a sling psychrometer?

One thermometer measures dry bulb temperature while the other measures wet bulb temperature. The difference between these readings indicates how much evaporative cooling is occurring and therefore provides information about the humidity of the surrounding air.

8. What happens when humidity is low?

When humidity is low, evaporation from the wet bulb occurs more rapidly. This causes greater cooling and creates a larger difference between the wet bulb and dry bulb readings.

9. What happens when humidity is high?

When humidity is high, less water can evaporate from the wet bulb. The wet bulb temperature therefore remains closer to the dry bulb temperature.

10. What happens when relative humidity reaches 100 percent?

At saturation, the wet bulb and dry bulb temperatures become equal because evaporation no longer produces significant cooling.

11. Is the RT-078 available with alcohol filling?

Yes. R-Tek offers an RT-078 Alcohol Filled Sling Psychrometer using red alcohol as the indicating fluid.

12. Is the RT-078 available with mercury filling?

Yes. R-Tek also lists an RT-078 Mercury Filled Sling Psychrometer with mercury as the indicating fluid.

13. Does the RT-078 have a Fahrenheit scale?

Yes. The official specifications state Centigrade and Fahrenheit as the scale types for both versions.

14. Is the RT-078 suitable for HVAC applications?

A sling psychrometer can be useful for HVAC work because wet bulb, dry bulb and relative humidity measurements are important when evaluating air conditions. R-Tek does not specifically list HVAC as an application for the RT-078, so this is a general application based on the instrument type.

15. Is the RT-078 suitable for laboratory use?

It can be used for general laboratory temperature and humidity observation where a manual sling psychrometer is appropriate. Any requirement for traceable calibration or a specified laboratory accuracy should be separately confirmed.

16. Can the RT-078 be used in warehouses?

A sling psychrometer can be used to spot-check temperature and relative humidity in warehouses and storage areas. This can help users understand environmental conditions affecting stored materials.

17. Is the RT-078 a digital humidity meter?

No digital display or electronic humidity sensor is specified on the R-Tek product page. The RT-078 is presented as a conventional sling psychrometer using indicating fluid thermometers.

18. Does the RT-078 require a battery?

The official RT-078 specifications do not mention a battery or electrical power requirement. It is listed as a conventional manual sling psychrometer.

19. What is the difference between a sling psychrometer and a digital hygrometer?

A sling psychrometer determines humidity from wet bulb and dry bulb temperature measurements and evaporative cooling. A digital hygrometer normally uses an electronic humidity sensor and displays relative humidity directly.

20. What is another name for a sling psychrometer?

Buyers may also search for this type of instrument using terms such as whirling psychrometer, wet and dry bulb psychrometer, manual psychrometer, sling hygrometer, whirling hygrometer and portable psychrometer. These terms are useful supporting phrases for the RT-078 product page because they describe closely related instrument terminology.