The Positives of Negative Checkweighing
Checkweighing is a standard feature found on most industrial-grade scales. Whether you are checking the weight of machinery parts, or checking the weight of ingredients to make a cake, you are likely to use this feature on a regular basis.
Operators use scales for checkweighing day-in-and-day-out, yet many do not realise that their scale has an inverse checkweighing feature. Let alone the benefits that can be had by using this over standard checkweighing.
Learn more about the advantages of negative checkweighing for your business.
What is negative checkweighing?
Negative checkweighing is a process performed on a scale or balance that works in a negative weight range. A total amount is placed onto the scale and tared to zero. Operators can then remove smaller amounts from the container as required. For example, if you have a large container of screws weighing 1kg and want to bag screws into groups of 100g, then you would tare the whole container so this shows as 0g on the scale display. From here, you would remove 100g each time so you should see amounts of -100g appear on the scale display per bag.
Checkweighing lights or alarms alert the user to the amount of weight remaining on the scale. Stating whether this is under, over, or of optimum weight in reference to pre-set weight limits.
How does negative checkweighing work?
Negative checkweighing works the same as a standard checkweighing procedure albeit in reverse. So, in standard checkweighing, an operator would pre-set a weight limit on the scale and then add weight until meeting the specified limit. If an item does not meet the set limit, checkweighing alarms or lights will state this.
Adam checkweighing scales have an LED back-lit, traffic light system for weight. Underweight items show as orange, overweight items show as red, and optimum weight shows in green on the scale’s display. You can see the LED checkweighing feature in action on Adam’s AE403 indicator video:
In negative checkweighing, you start with a total weight on the scale. You can then remove amounts of product until reaching a pre-set negative weight limit. The scale may sound an alarm or have a back-light that illuminates green once you have reached the pre-set weight limit.
This step-by-step guide uses an Adam checkweighing scale to show how negative checkweighing works:
- Place a total amount onto the scale.
- Tare the scale.
- Once tared, remove parts from the scale until you have reached the target amount. (This will then show as a negative amount).
- Tare again to reset to zero.
Does negative checkweighing work on a counting scale?
Yes! Counting scales work in units and a unit weight limit needs to be set before counting. Negative counting scales are like negative checkweighers, although weight is measured in number of parts.
Which is best: negative checkweighing or negative counting?
Most manufacturers find negative counting quicker and easier. Negative counting uses number of pieces rather than weight removed from a total. For example, would you find it easier to say that 50 screws need removing from that box or 65g of screws (1.3g per screw) need removing from that box?
When you might use negative checkweighing
The automotive industry have large-scale manufacturing processes. These processes need to be efficient while retaining immaculate levels of accuracy and precision. Engineers use many tools to maintain this standard, one of which is the weighing scale.
Negative checkweighing and parts counting scales are often found in product testing areas. They ensure that bolts or small parts are quality-checked, present and accounted for. Each piece is weighed to ensure safety and construction requirements are maintained. An inaccurate count or weight many highlight material defects or cause them later in the manufacturing process.
Large-scale industries will import materials in bulk within boxes and containers. Usually, they will specify the amount of pieces or weight contained within a box on an exterior printed label. Checkweighing allows the operator to place whole boxes of pieces onto a scale in one go to verify weight. Operators can then remove the amount of parts needed each time, based on a subtraction of weight from the box. These parts are then gathered into smaller amounts needed for the vehicle assembly process.
(Note: If you are using a scale with parts counting you can calculate a weight per unit and remove a certain number of pieces).
Food processing & preparation
Restaurants can use negative checkweighing for measuring cooking ingredients and portion sizes. Pizzerias can place containers of ingredients such as cheese, tomatoes and onions onto a scale. From here, they can then remove handfuls of each ingredients for each pizza. With negative checkweighing, chefs can see if they have used too much or too little. This is especially useful for food chains that like to work to a standardised recipe or formula.
Caterers can use negative checkweighing to track the amount of flour, sugar and other ingredients in recipes. This ensures that amounts do not fluctuate from a recipe when working in batches. Negative checkweighing ensures an even distribution of ingredients per batch. If you have a total of 5kg of flour on the scale and you know you need 5 batches, you can calculate how much flour you need to remove from the container for each batch.
Working without a weighing scale in the food industry can effect taste, consistency and quality; thus impacting brand reputation!
See our previous articles to learn more about how to use weighing scales in the food industry:
Retail warehouses & stores
Through negative checkweighing you can remove exactly the right amount of parts you need and place these into bags. Once packaged, you can use trade approved scales to re-weigh these bags to ensure they meet legal standards for selling by weight in shops.
So why is the negative checkweighing feature important?
By this point I’m hoping many of you will have realised the limitless benefits of using this often ignored feature. The negative checkweighing feature simplifies labour cost by adding the total amount of product to the scale and then removing amounts as you go. Ideal for any business that weighs huge amounts of single products such as coffee beans, sweets, vegetables, screws and other parts.
Things to consider when buying a scale with negative checkweighing
- Negative checkweighing is NOT allowed on trade approved scales. So, if you need a scale that is trade approved, make sure that you do not need the negative checkweighing feature to sell products by weight.
- Weight capacity – You need to ensure that you are buying a checkweighing scale that meets your weight requirements. We recommend choosing a scale that gives you around 50% extra weight capacity than what you need. This ensures that you have that extra bit of space to manoeuvre if you start working with larger batches of products.
- Resolution – Weighing scale resolution (readability) is crucial for operators that weigh lightweight items. If you need a high-level of precision, we recommend a scale with a higher resolution than your standard checkweigher. Many precision balances offer checkweighing functions and can have anything between 0.01 to 0.0001g resolutions.
Inscale’s selection of negative checkweighing scales
The GBK bench checkweighing scale has a grade 304 stainless steel construction and can withstand rigorous use in industrial environments. Designed for a bench-top surface, the scale includes negative checkweighing for small parts and tools.
Designed for a factory or warehouse floor. The GFK offers higher weight capacities than bench scale models. The GFK includes negative checkweighing for weighing large containers that cannot be easily be lifted. This scale is ideal for weighing and counting heavy machinery parts in vehicle manufacturing.
A tried and tested Adam Equipment product that is both versatile and durable in design. The CBK bench checkweighing scale is a firm favourite of manufacturers and engineers. Used for checkweighing small parts such as screws, tools and bolts. CBK has both negative checkweighing and negative counting operations, allowing operators to count pieces with exceptional accuracy and speed. This scale offers trade approved models for selling by weight.
Adam Equipment's AE403 weight indicator ideal for keeping check of warehouse stock levels. Connect the indicator to Adam platform scales for enhanced weighing functions. Negative checkweighing can be set on the AE403, allowing operators to manage huge containers of parts. Stainless steel construction and IP67-rated housing offers advanced protection against dust and water.