WWA-1 evaluation device with dosing function

Our WWA-1 indicator is available with the WWC-4N relay box. This allows it to be used for simple dosing functions, target weighing (checkweigh function), and other switching functions.

Dosing

The WWC-4N relay box features four potential-free relays. This allows up to four different components to be dosed. Operation of the WWA-1 is very simple and intuitive. The user can determine whether one, two, three, or four components should be controlled. The components can be dosed automatically one after the other or started individually. An automatic overrun correction for each component can be activated. This determines how much has continued to run after the valve or a screw has been switched off. In subsequent dosing cycles, the system then switches off earlier accordingly to ensure the target weight is precisely reached.
An adjustable maximum weight (maximum container capacity) prevents overfilling. Furthermore, the system checks whether the component is actually flowing in. If no weight increase occurs within a certain time period while the component is switched on, the process is stopped.
Of course, the dosage can also be paused, continued or stopped at the push of a button.

In the following videos we show different dosing options.

1. Dose a component

In the video, 500 kg is initially dosed. Then, the target value is changed to 400 kg and the dose is again added. Dosing is paused briefly in between.

2. Dose three components separately

After starting, you'll be asked which of the three components you want to dose. After selecting 1, 2, or 3, the respective dosing starts. At the end of the video, you'll see how to change the target value for component 1 from 250 to 200 kg.

By the way, this function allows you to dose up to four stored weights. For example, if you have big bags that always need to be filled with 1000, 750, 500, or 250 kg, you can set the target value for component 1 to 1000 kg, for component 2 to 750 kg, for component 3 to 500 kg, and for component 4 to 250 kg. The relay box connects everything so that the same feed screw is started for all four components. On the device, you simply select component 1, 2, 3, or 4, start it, and 1000, 750, 500, or 250 kg will be filled.

3. Automatically dose four components one after the other

With this dosing method, four components are automatically added one after the other. At the end, we'll also show you how to change the target value for a component.

Dosing

Dispensing differs little from filling. The target values to be dispensed from a container are edited as described in the videos above. When the program is started, the selected weight is dispensed from the full container. If the container weight falls below the target weight, the weight flashes and the program cannot be restarted.

Semi-automatic filling control with the 83sigma evaluation device

We also implement simple dosing systems with our evaluation devices and electronics. One example is semi-automatic filling control. The goal is to fill a specific quantity as accurately as possible. This is often achieved with a feed screw whose motor is controlled by a frequency converter. The screw conveys the material into a big bag, sack, or container. The big bag can be suspended from four load cells or stand on a weighing bridge. Smaller bags or containers are weighed on a weighing bridge with a single-point load cell.

Our example demonstrates the simple operation of such a control system with the 83sigma evaluation unit . This requires the evaluation unit with enabled inputs and outputs and the HAS program. The outputs control a relay card, which in turn controls the frequency converter in a small control cabinet. A button can be connected to one of the inputs to start the filling process. The second input can be used as a safety feature for a quick termination.

The HAS (semi-automatic filling control) program monitors the filling of a specified material quantity (setpoint) of a component after startup. If the target range (net weight between the - and + tolerance limits) and the idle position (switchable) are reached during a filling process, the process is automatically terminated and the outputs deactivated. In addition to the - and + tolerance limits, there is also the -- tolerance limit. This determines the switching of the frequency converter from coarse to fine flow, so that the feed screw rotates more slowly at the end of the dosing process.

The 6 function keys of the 83sigma are assigned as follows by default:

• F1 = Start filling with previous entry of the target value
• F2 = Start filling with the last used target value
• F3 = Pause filling
• F4 = Continue filling
• F5 = Change target value and tolerances
• F6 = Cancel

Example:

A big bag is to be filled with 1000 kg. The filling tolerance should be between -0.5 kg and +1 kg, meaning the target value is between 999.5 and 1001 kg. Switching from coarse to fine flow should occur at 990 kg.

First, the target value and tolerances must be entered into the device. To do so, press the F5 key. The following information will be requested:

Target value = 1000kg
Tolerance -- = 10kg (switching at 990kg from coarse to fine flow)
Tolerance - = 0.5kg
Tolerance + = 1kg

The filling process can then be started with the previously set parameters using the F2 key (or the button at input 1).

Pressing F1 will first prompt you for the target value to be filled. Confirmation will start the filling process immediately. The most recently defined tolerances will be used.

The process can be paused with F3 and continued with F4.

F6 (input 2) aborts the entire filling process.

Further settings allow you to specify whether taring should be performed before filling. If necessary, the filled weights can be totaled, printed, and/or sent to a PC. Manual refilling is also possible.

Under certain conditions, this system can also be used as a calibrated non-automatic weighing instrument. Ask us...

If several components are to be filled, the 84vario with the recipe program is required.