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.

Which Conductivity Sensor Suits Your Application? (Part II)

In part one, we discussed measuring conductivity. Here, we continue with high purity applications and other special applications.

Low-Conductivity and High-Purity Applications

Temperature greatly influences conductivity; generally the colder the water, the lower the conductivity. “Measuring the low end of conductivity is tricky,” said Frank Paparone, Global Product Manager for Water Analysis Instruments, Thermo Fisher Scientific.

“Since temperature can vary the result by 5% or more per ºC, it’s important to use the correct compensation factor or none at all,” he said. “Electrodes with low cell constant values incorporate improved designs allowing the sensors to be more sensitive in low ranges. When carbon dioxide in air causes variations, a universal flow-through adapter will help. When conductivity is used as a relative measurement—comparing two samples or identifying trends up or down—it is quite a bit easier than using conductivity as an absolute measurement, particularly in pure water.”

High-purity water (0.055 to 1 µS/cm) is used to produce pharmaceuticals, cosmetics, food, semiconductors, and more. When measuring high-purity water, the inverse of conductivity, “resistivity,” is the norm.

Greater Compatibility with Solvents

Glass electrodes can handle high temperatures and are compatible with solvents. They are also easy to clean yet they are breakable. Plastic electrodes do not break, but can’t be used in the presence of solvents because of chemical attack that can occur on the plastic and also have temperature limitations.

“For a robust electrode with repeatable results that lasts longer and can be used with many acids, consider a graphite sensor,” said Paparone. “It is more expensive but graphite is both easy to clean and compatible with most solvents.”

High-Salt Solutions

“If you double the amount of salt in solution, you will roughly double the conductivity, but only to a point. If sample dilution isn’t desirable, consider ditching traditional conductivity measurements for a hydrometer, which is based on density,”said Paparone. “Conductivity meters are best for solutions containing less than 5% salt.”

For solutions that meet this requirement, but would still be considered on the high end of the salt range, a torodial conductivity transmitter may work best. It is an industrial transmitter with an electrodeless sensor. High-salt applications in the food industry—for example, using brine solutions or a plating bath—utilize this technology for their measurements. Electrodeless sensors eliminate contamination and reduce long-term maintenance costs.

Small Volumes and Large Volumes

A microprobe (or microsensor) or a flow-through electrode can be used in small sample sizes measured in vials or well plates. For large-volume samples, some pharmaceutical facilities use industrial cell types with fittings that connect to tanks or pipes.

Watch for part three of this article posted on Friday.

View our selection of conductivity meters, testers and electrodes and sensors.

Which Conductivity Sensor Suits Your Application? (Part II)

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