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 2)

In part one, we named three technologies for measuring dissolved oxygen: Polarographic, Galvanic, and Optical. After discussing Polarographic and Galvanic, read below for more on Optical technology.

Optical

The optical detection of dissolved oxygen is based on the principle that dissolved oxygen quenches the luminescence associated with the chemical dyes in the sensor. The probe measures dissolved oxygen by emitting a blue light that causes the sensing element to luminesce (glow red). The luminescence is inversely proportional to the level of dissolved oxygen present (based on Stern-Volmer relationship). When no oxygen is present, the luminescence signal is at its maximum; and as oxygen is introduced, the luminescence decreases.

Three ways of measuring optical dissolved oxygen are the magnitude domain, time domain, and phase domain. Magnitude measures the peak height of luminescence. Accuracy degrades over time as the sensor degrades due to photo-bleaching; frequent calibration is required for this method. The time domain measures the decay rate of luminescence. Signal-to-noise ratio can limit the sensor range in this method. The phase domain (phase detector) measures the phase difference based on the entire signal and reference wave forms across a population of pulses. This method delivers the highest accuracy over the widest operating range and is commonly applied.

Optical meters provide the convenience of no membrane replacement, no electrolyte replacement, no incoming flow required, and no hydrogen sulfide interference. The meters also offer a short response time, minimal drift, and minimal maintenance. Exposure to alcohols and other organics must be limited to avoid damage to the sensor.

All three technologies offer viable methods for detecting dissolved oxygen. However, the convenience and accuracy of optical dissolved oxygen is winning over operators.

View our selection of dissolved oxygen meters.

Three Dissolved Oxygen Technologies: Which Works Best for You? (Part 2)

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