GMC-X3 Loss-in-Weight Controller
Quick specs
| I/O & Performance | |
|---|---|
| Inputs | 4 fixed digital inputs + 4 freely-defined I/O (up to 8 inputs total); opto-isolated, low-level effective |
| Outputs | 4 fixed digital outputs + 4 freely-defined I/O (up to 8 outputs total); transistor open-collector, 200 mA drive current |
| Communication | 1× RS-485 + 1× RS-232 standard (Modbus-RTU, continuous, print); 1 analog output standard; optional 1 analog input (current/voltage selectable); optional dual Ethernet (Modbus-TCP) or Profinet bus interface; USB for parameter import/export |
| A/D speed | 24-bit; 480 SPS sampling speed |
| Resolution | 1 / 100,000 (max display); input sensitivity 0.1 µV/d; non-linearity 0.01% F.S; gain drift 10 PPM/℃ |
| Connection | |
| Display | 160×128 1.96" white OLED display; 6-key sounding keyboard; 5 decimal point positions (0 / 0.0 / 0.00 / 0.000 / 0.0000); OFL overload indication |
| Load cell excitation | DC 5 V, 200 mA max (supports up to 8 × 350 Ω load cells; 1mV/V, 2mV/V, 3mV/V sensitivity) |
| Physical & Environment | |
| Power supply | 24 VDC (18 – 30 VDC), 15 W max |
| Operating temperature | Certified: -10 ℃ to +40 ℃ · Operating: -20 ℃ to +60 ℃ · Storage: -40 ℃ to +60 ℃ |
| Operating humidity | ≤90% RH, non-condensing |
| Enclosure | Panel-mount compact controller |
| Dimensions | 62 × 134 × 127.5 mm (W × H × D); ~886 g |
Applications
- Plastics extrusion feeding
- Chemical compounding
- Food ingredient dosing
- Powder and granule continuous feeding
OEM & ODM ready
Built for integration into your line, your machine, or your brand.
As General Measure’s South African partner, R&D Weighing supports OEM and ODM engagements across the controller range. From private-label badging through to custom enclosures, communication protocols, and full system integration with your existing PLC, MES, or ERP environment.
- Private-label finishing & branding
- Custom enclosure & mounting options
- PLC / MES / ERP integration
- Bespoke communication / protocol configurations
- Multi-line synchronisation
- Engineering support throughout commissioning
The loss-in-weight controller GMC-X3 manages continuous gravimetric feeding of bulk solids: plastic pellets into an extruder, food powders into a mixer, chemical powders into a reactor, mineral feed into a calciner. Unlike a batching controller that dispenses discrete cycles, the X3 maintains a continuous setpoint mass flow by modulating the speed of a screw, vibratory or rotary feeder based on the rate of weight loss from the supply hopper above the feeder.
Continuous gravimetric feeding for process applications
Many continuous processes need a constant mass flow of one material into a mixing, reaction or extrusion process. Say, 50 kg/hour of titanium dioxide pigment into a plastic compounding extruder. Volumetric feeders (just running a screw at constant speed) drift as material bulk density varies. A loss-in-weight controller closes the loop: it tracks the rate of weight loss from the hopper above the feeder, compares it to the setpoint mass flow, and modulates feeder speed in real time to hold the setpoint regardless of bulk density variation. The result is mass-accurate continuous feeding to within fractions of a percent of setpoint.
Hopper refill and feeder modulation
A loss-in-weight controller has to manage two complications: the hopper must be refilled periodically (which destroys the weight-loss signal during refill), and the feeder speed must respond fast enough to correct setpoint deviations without oscillating. The GMC-X3 handles both. Refill detection automatically switches the controller into volumetric (open-loop) mode during refill and back into gravimetric mode when refill ends, while a tuned PID loop modulates feeder speed for fast setpoint recovery without overshoot.
Frequently asked questions
When should I use a loss-in-weight feeder instead of a volumetric feeder?
Use loss-in-weight feeding when mass-flow accuracy matters. Typically for ingredients whose dosing ratio drives product quality (pigments and additives in plastics, vitamins and minerals in feed, catalysts in chemical reactions). Volumetric feeders are fine for non-critical bulk ingredients or when the downstream process is insensitive to feed rate variation.
What kinds of feeders does the GMC-X3 drive?
Single- and twin-screw feeders, vibratory feeders, rotary valves and modulating belt feeders. The X3 outputs a variable analogue control signal (typically 4-20 mA) that the feeder VFD or motor controller uses to modulate speed proportionally to the setpoint flow demand.
How does the GMC-X3 handle hopper refill?
Refill is detected automatically when the supply hopper weight starts to rise. During refill the controller switches to volumetric mode (last-known feeder speed), then switches back to gravimetric mode when the hopper weight stabilises after refill. The transition is automatic. No operator intervention needed.
