7 Possible Reasons Your Laboratory Balance is Giving Different Readings Every Time

There comes a time in every laboratory’s life when they just can’t seem to obtain accurate results from their balance. There are a variety of reasons this might happen, and, luckily, a variety of tips, tricks and solutions to help prevent them from happening again. Let’s get into the top seven most common.

1.    Out of Calibration

One reason why your balance keeps giving different readings is because it requires a fresh calibration. Even if you have a regular calibration schedule, there are a few instances that may alter the balance enough to require a new calibration, including:

• After moving the laboratory balance to a new weighing environment (even if it's just another room!)
• After jolting or jostling the balance
• After any repairs or internal work

You can learn more about why in our previous blog, “How Often Do I Need to Calibrate My Weighing Scale?”

In general, the finer the readability on your laboratory balance, the more often we recommend calibrating – especially before any major weighing sessions. Many Adam lab balances offer models with both internal and external calibration options. Both are incredibly reliable for regular use, though if you prefer to calibrate internally, we still recommend keeping a test weight nearby. It’s excellent for quick and easy verification that your balance is accurate between calibrations.

If you calibrate your balance and it’s still acting up, consider whether your laboratory is suffering from drafts. 

1.    Drafts

Semi-micro and analytical balances are always fit with a draft shield to protect your results against air currents. It’s critical to close the draft shield after placing an item on the pan, even if the action gets tedious after a while. Other balances, like precision balances, may or may not offer a draft shield, in which case it’s more important to be careful.  Air currents can interfere with the amount of force enacted on the item you’re weighing, whether it lifts the item from the pan or blows particles away.

Even when utilising the draft shields correctly, it’s still a good idea to keep your balance away from windows, air conditioning units or doors that are frequently opened and closed! Try moving your balance to a draft-less location and/or ensuring that you close the draft shield doors before, during and after each use.

2.    Vibration

Vibrations are very common in laboratories, though you may not notice them unless you’re really paying attention. Heavy footsteps, construction down the street, doors slamming, the ventilation system turning on and off – all cause vibrations that may prevent your balance from settling properly.

Luckily, this particular issue is easier to solve. Adam offers an AVT Anti-Vibration Table.  It's a table-top with an independently supported block of heavy granite in the middle. The granite is so thick, heavy and solid that it neutralises vibrations. Unless there’s an earthquake, your results should stabilise more effectively.

3.    Static

Static is difficult to diagnose – you may notice your balance acting oddly, refusing to settle, or changing the display even with nothing on the pan. Take note – are you using rubber gloves? Plastic containers? Dragging items on and off the pan instead of setting and lifting them directly? How about materials – do you often weigh powders, or fabrics? These are all common ways that static could generate. Perform research on how you can best ground your environment to reduce static. 

If the answer to all the above is a big fat NO, consider the humidity level of your laboratory. Static builds more easily in extremely dry environments. To help prevent static from generating, ensure you always keep your laboratory at a humidity level of around 40%.

4.    Lack of Warm-Up Time

Did you know that before you use your laboratory balance for the first time in a new environment, you’re supposed to let it warm up? And by warm up, we mean literally – adjusting to the temperature and conditions of your environment. Scaletec recommends letting the balance warm up at least 12 hours before use. Of course, you can do this overnight, and you don't have to keep your laboratory balance on the whole time. Ensure you calibrate after those 12 hours!

5.    Dirty Pans

When’s the last time you gave your balance a cleaning? Oils, leftover particles and dust are often known to gather in large quantities on and around the weighing pan before they’re obviously noticeable. Eventually they can begin to disrupt your results, especially with semi-micro balances like Adam’s new Polaris PAB 125i.

It’s important not to use any cleaning tools that will leave a residue themselves, like paper towels. A soft bristled brush to sweep away any solid particles can be useful. For liquid or sticky residue, consider an ethanol-based cleanser and a microfibre cloth. Always double check after cleaning that nothing has been left behind in the process!

6.    Temperature Changes

Did you know that significant temperature changes in a room can cause your results to become inconsistent? When you cali in one environment and temperature, it can become ‘confused’ when this changes. If the temperature gets lower, the metals and plastics in the balance could begin to contract, whereas if it gets higher, they could begin to expand. Keep your balance out of direct sunlight so this doesn't speed up the process.

Also keep in mind that your samples and your balance should be at the same temperature before they’re weighed whenever possible. For example, if you know that you’re going to be weighing an item later in the day, keep it close to the balance so they equalize at the same temperature. This helps prevent convection currents from forming in your draft shield. That’s especially risky, as it negates the purpose of the draft shield and may potentially cause the pan or your sample to shift, altering your results.

Even the balances, if used for a long enough span of time, can begin to generate their own heat from the internal mechanisms warming up. Kind of like how your phone gets warm when you’re using it for a while. The heat generated from the balance can rise up, pushing on the weighing pan and into the weighing chamber. Luckily, Adam’s new Polaris PAB 125i offers a special feature. It’s called Air Diversion Technology, or ADT, and it helps divert the warm air from the weighing pan so it doesn’t push up and impact your results!  

If you’ve checked all the possible causes of your inaccurate results and you’re still having problems getting consistent readings, you can contact the Scaletec team for help.