Today’s review is on the 9535 / 9535-A Velocicalc Air Velocity Meter from TSI Incorporated. TSI is a global market leader in Air Flow Measurement, Indoor Air Quality, and many other Research Quality Testing and Monitoring instruments.

What is an Air Velocity Meter

Air Velocity Meters are usually handheld instruments that include a probe that, at the minimum, measure Face Air Velocity and Air Temperature.  Face Velocity is a term used to describe the air flow, say from a vent, that directly hits the sensor of your probe. If you have a straight probe, you will have point the probe directly into air flow to get an accurate measurement.

An articulated probe is similar to a straight fixed probe except that it has a joint where you can bend the probe if necessary. The sensor is still fixed and will have to meet the air flow directly on its “face” to get the most accurate air velocity measurement. Temperature measurement is pretty straight forward in that it will give you the temperature of the air that is contacting the sensor. You will again want the air flow to be hitting the sensor to make sure you are getting the most accurate measurements.

Air Velocity Meters can normally handle Volumetric Flowrate but it is a calculated value instead of a directly measured one. Air Velocity Meters calculate the estimated air flow using a formula of sorts. The user will go to the settings and select the volume test and will be prompted to input the dimensions of the duct or whatever you are measuring. Then multiple air velocity measurements are taken within the ductwork. The meter will then works its mathematical magic and give an estimated volume flow.

If you are interested in measuring Air Flow Volume with more certainty, I would recommend looking at an Air Flow Hood or commonly referred to as a Balometer.

Specifications of the TSI 9535 and TSI 9535-A

The specific models TSI 9535 and TSI 9535-A can be referred to as the middle entry for handheld air velocity meters from TSI. They offer more features than the 9515 but there are a few deviations from the 9545 and 9545-A version of this instrument. The only difference between the 9535 and the 9535-A is the probe type. The 9535 uses a standard straight probe and the 9535-A includes the Articulating Probe. As discussed earlier, the articulating probe has a knuckle joint about 8” from the tip that allows it to bend 90 degrees. This gives the probe a little more flexibility over the fixed straight probe in small or tight spaces. The units themselves perform the same functions which are as follows,

• Velocity: 0-6,000 ft/min (0 to 30 m/s) with an accuracy of +/- 3% of the reading or +/- 3 ft, whichever is greater. Has a display resolution of 1 ft/min (0.01 m/s)
• Volumetric Flow Rate: Function of the velocity and duct size
• Temperature: 0-200 Degrees Fahrenheit, Accuracy +/- 0.5 Degree Fahrenheit. Display resolution 0.1 Degrees Fahrenheit
• Manual Datalogging as well as LogDat2 downloading software

Wrap Up

The TSI 9535 and 9535-A Air Velocity Meters are excellent small and lightweight (0.6lbs) meters that make quick work of most diagnostics for hvac system performance, duct transverses or any other function where you need to measure air velocity and air temperature. They are easy to operate and the screen is easy to read with large clear numbers. Are you happy with your current Air Velocity Meter? What is the biggest frustration you have that can be improved?