Spectrex - Precision Pocket Bubble Flow Meters for Air Sampling
These unique units are: Portable (Weights: 1.5 oz; 2 oz; 8 oz.), Self-contained, Leakproof, All plastic, Provide instant soap bubble movement by depressing central cylinder 1/4`. Flow is established by timing bubble and reading off flow from a special `time` chart attached to the flow meter barrel.
Abstract of Paper from San Diego State University Masters Program
Bubble flow meters, both the electronic and standard soap bubble meters, are the most common primary standard air flow rate calibration instruments used today in industrial hygiene, with accuracies of less than + - 1.0%.
The electronic bubble meters are relatively expensive, battery operated, must be maintained and have problems upon repeated use. The standard soap bubble meters are very fragile, relatively non-portable and awkward to use. Associated accuracies of both types of devices are
Pocket bubble flow meters are small versions of the standard soap bubble meter. They are compact, portable, simple to use, inexpensive and an accuracy of + - 2.0% is reported by the manufacturer.
The primary focus of this study is to compare the performance of the pocket bubble flow meters to a primary standard bubble flow meter to determine whether the pocket bubble flow meters would be an acceptable substitute without greatly increasing the total error in flow rate measurements.
The pocket bubble flow meters, of which the three different model sizes from this manufacturer were included in this study, were connected in series with an electronic bubble flow meter to an air flow source. Sets of 100 paired data points were collected over flow rates between 10 and 2000 ml/min. The average flowrates, standard deviations, percent relative standard deviations and percent accuracies were calculated.
The meters perfomed well within the accuracy reported by the manufacturer. Average accuracies of less than 1.0% were obtained using the meters, except for one test in which the results were in question. These results are all within OSHA’s accuracy limit of 5%. The majority of the devices average flow rates were within one standard deviation of the electronic bubble flow meters average flow rates. The meters were reliable with precision values of less than 1.0% for all flow rate tests conducted, and are within OSHA’s precision limit for flow rate measurements.
Paired two-tailed t-tests were performed on the sets of data and a statistical difference was determined at the 0.05 level of significance. These differences are very small, would not negatively affect sampling results and are scientifically insignificant.
It was concluded that the Pocket Bubble Flow Meters are acceptable substitutes for the electronic or standard soap bubble meters when used appropriately and with care.