What is the difference between an analytical balance and a precision balance?

An analytical balance provides readability of 0.1 mg or better, while a precision balance typically reads to 0.001 g or 0.01 g. Analytical balances include draft shields and are designed for highly sensitive measurements. Precision balances handle larger samples and are less affected by environmental conditions.

What readability do I need for my lab application?

You need a readability that is at least one-tenth of your smallest sample weight or required measurement increment. For example, measuring 100 mg samples may require 0.01 mg readability, while gram-level work may only need 0.01 g. Selecting higher readability than necessary increases cost without improving results.

Do lab balances need to be calibrated?

Yes, all lab balances require regular calibration to maintain accuracy. Calibration ensures measurements remain traceable to certified standards. Internal calibration simplifies this process by automating adjustments, while external calibration requires manual verification with certified weights. In regulated environments, calibration records must be documented and retained.

What is the difference between readability and repeatability?

Readability is the smallest increment of weight a balance will display. Repeatability is the degree of agreement between multiple measurements of the same mass, on the same balance, under the same conditions.

What is the best way to clean my balance to ensure accurate readings?

Inspect and clean before each use. A flannel cloth or soft brush works well for dusting and light cleaning. Use a non-abrasive cleaner for light spills, and a dry flannel cloth for glass parts. Set a regular maintenance schedule for deep cleaning to ensure optimal performance and instrument longevity.

Can vibration affect the accuracy of my balance?

Yes — even slight vibration from a heavy footstep can affect accuracy. Place the balance on a sturdy benchtop away from high-traffic areas such as hallways, elevators, stairways, and doors. If that placement is not possible, an anti-vibration table should be considered.

Three Dissolved Oxygen Technologies: Which Works Best for You? (Part 1)

Dissolved oxygen is a critical measurement for wastewater treatment. An operator must ensure proper aeration for the aerobic bacteria in the tank to break down organic suspended solids. Three technologies for measuring dissolved oxygen are employed in the market today: Polarographic, Galvanic, and Optical.

Polarographic

Clark-cell, polarographic technology supplies constant electrical voltage across the anode and cathode. As oxygen is reduced, the current supplied to the cathode is increased. The amount of electricity required to reduce the oxygen at the cathode is equivalent to the dissolved oxygen present.

This technology was developed in 1956 and is familiar to most operators. The challenges of polarographic technology include necessary warm-up time, membrane replacement, and the potential of electrolyte solutions degrading.

Galvanic

Galvanic technology, developed in 1964, consists of an anode and cathode in electrolyte solution covered with an oxygen-permeable membrane. As oxygen permeates the membrane, the cathode reduces the oxygen, creating a potential that is equal to the amount of oxygen in the system.

This method offers the advantages of eliminating warm-up times, as the self-polarized probe is ready to read. However, galvanic technology still struggles with membranes and electrolyte solutions. Interference occurs with the presence of any chemical that produces an electrical charge.

Look for part II to read about optical dissolved oxygen technology.

Three Dissolved Oxygen Technologies: Which Works Best for You? (Part 1)

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