Weight-Based Products System

Complete Help & Documentation Center

System Overview

What is This?

The Weight-Based Products system enables your store to sell items like meat, fruits, and vegetables by weight using EAN-13 barcodes that encode both product identity and weight.

Key Features
  • EAN-13 compatible barcodes
  • Weight embedded in barcode
  • Automatic price calculation
  • Tare weight handling
  • Works with any compatible scale
How It Works
  1. Create Products: Configure weight-based products with pricing and tare weights
  2. Export to Scale: Download CSV and import to your label-printing scale
  3. Weigh Items: Staff weighs items and scale generates barcodes automatically
  4. Scan at Checkout: POS reads barcode, extracts weight, calculates price
  5. Complete Sale: Customer pays the exact amount for the exact weight

Barcode Format

2 0 1 2 3 4 5 0 1 5 0 0 7
20

Type
(Meat)

12345

Product
Code

01500

Weight
(1500g)

7

Check
Digit

Product Categories

??
Meat (20)
??
Fruits (21)
??
Vegetables (22)
??
Dairy (23)
??
Bakery (24)

Complete Documentation

Setup Guide

Complete step-by-step instructions to set up the system from scratch. Covers database migration, product creation, testing, and deployment.

Open Setup Guide

Scale Integration Guide

How to integrate with different types of scales. Covers label-printing scales, external printers, Android/Tablet, and PC-based solutions.

Open Integration Guide

Configuration Templates

Specific setup instructions for popular scale models including CAS, Bizerba, Toledo, Avery Berkel, and Digi scales.

Open Configuration Guide

Technical Summary

In-depth technical documentation covering system architecture, database schema, API endpoints, and price calculation logic.

Open Technical Docs

Staff Quick Reference

Simple guide for counter staff. Print and laminate for quick access at butchery, produce, and deli counters.

Open Quick Reference

Complete Documentation Index

Master index with links to all documentation, quick start guide, and navigation to specific topics.

Open Master Index

Quick Start (30 Minutes)

Prerequisites: CNPERP system running, PostgreSQL database configured, FastAPI server active on port 8010.

Add weight-based product fields to your database:

cd C:\dev\cnperp-python
.\.venv\Scripts\Activate.ps1
python add_weight_based_products.py
Expected: ? Weight-based product fields added successfully!

Create weight-based products:

  1. Open: Products Page
  2. Click "Add New Product"
  3. Fill in basic details (Name, SKU, Category)
  4. Check "Enable Weight-Based Selling"
  5. Select Product Type (Meat, Fruits, etc.)
  6. Enter 5-digit Product Code (e.g., 12345)
  7. Set Price per kg (e.g., 125.00)
  8. Set Tare weight if applicable (e.g., 50g for packaging)
  9. Save Product

Tip: Create 5-10 sample products to test with.

Option A: Web Generator

Open Barcode Generator

  1. Select a product from dropdown
  2. Enter weight (e.g., 1500 grams)
  3. Click "Generate Barcode Label"
  4. Verify barcode and price are correct
Option B: Scale Simulator
python scripts/scale_simulator.py

Follow interactive prompts to simulate complete workflow.

Export products to import into your scale:

All Products Meat Only Fruits Only Vegetables Only

Next: Import CSV to your scale via USB, Network, or manual entry. See Configuration Templates for your specific scale model.

Frequently Asked Questions

Q: What scales are compatible with this system?
A: Any label-printing scale that supports EAN-13 barcodes with configurable format. Popular models include CAS CL-5000, Bizerba GLMI-800, Mettler Toledo 8530, Avery Berkel HL122, and Digi SM-300. See the Scale Integration Guide for details.
Q: How is the price calculated?
A: Price = (Gross Weight - Tare Weight) × Price per kg
Example: 1500g gross - 50g tare = 1450g net = 1.45kg × R125/kg = R181.25
Q: What is tare weight?
A: Tare weight is the weight of packaging (tray, wrapper, container) that should not be charged to the customer. The system automatically subtracts this when calculating the price.
Q: Can I test without a physical scale?
A: Yes! Use the Barcode Generator web interface or run the scale simulator: python scripts/scale_simulator.py
Q: Why won't my barcode scan?
A: Common causes:
  • Scale configured for wrong barcode type (must be EAN-13, not CODE-128)
  • Checksum calculation not enabled in scale
  • Poor print quality - clean the printhead
  • Barcode too small or damaged
See the Troubleshooting Guide.
Q: How do I update prices on the scale?
A:
  1. Update prices in CNPERP products page
  2. Export new CSV: Download Here
  3. Import to scale via USB/Network
For automated sync, see the Network Scale Management section in the setup guide.
Q: What do the barcode prefixes mean?
A: The first 2 digits identify the product category:
  • 20 = Meat (Beef, Pork, Chicken, Lamb)
  • 21 = Fruits (Apples, Bananas, Oranges)
  • 22 = Vegetables (Tomatoes, Lettuce, Carrots)
  • 23 = Dairy (Cheese, Butter by weight)
  • 24 = Bakery (Bread, Cakes by weight)
Q: Can I use this for items sold by piece?
A: No, this system is specifically for weight-based products. For items sold by piece (count), use regular products with standard barcodes.

Tools & Utilities

Barcode Generator

Generate and print weight-based barcode labels for your counter staff.

Open Tool
Product Management

Create and configure weight-based products with pricing and constraints.

Manage Products
Export for Scale

Download CSV file to import products into your label-printing scale.

Download CSV

API Endpoints

Endpoint Method Description Action
/api/v1/weight-products/weight-products GET List all weight-based products (filter by category optional) Test
/api/v1/weight-products/parse-weight-barcode POST Parse barcode and return product with calculated price
/api/v1/weight-products/export-for-scale GET Export products as CSV for scale import Download
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