Certindo Worksheet — calibration data, entered once.

What the project is

Certindo's calibration technicians traditionally recorded measurements on paper and later entered the same information again into Excel. Beyond the repeated work, each instrument used its own worksheet structure, making a single generic export insufficient for the real process.

How I approached it

I designed the internal tool around the existing calibration workflow instead of forcing every instrument into one form. Technicians can search the worksheet catalog, select the correct instrument template, enter structured record and measurement data, save their progress, and export the result when it is ready.

From interface to system

I built the system as a TypeScript monorepo with a Next.js frontend, NestJS API, and PostgreSQL through Prisma. The main challenge was translating 91 existing Excel templates into reliable mappings one by one: identity fields, individual cells, conditional and composite values, and measurement tables all had to land in the correct workbook positions while preserving each source template. A worksheet cannot be exported until its mapping has been verified.

How the pieces connect

A simplified view of the implemented product flow—not a claim about infrastructure that is not public.

1. 01

   Choose

   Find the correct instrument-specific worksheet

   Next.js
2. 02

   Record

   Capture identity, conditions, and measurement data

   NestJSPostgreSQL
3. 03

   Map

   Apply verified cell and table rules for each template

   Prisma
4. 04

   Export

   Preserve the original workbook structure for delivery

   JSZipExcel

What changed

The internal system turns the former paper-to-Excel handoff into a single digital flow. Calibration data can be recorded, edited, tracked, and exported directly into the appropriate Excel worksheet without manually entering the same values for a second time.

What I learned

This project showed me that workflow automation depends on detail as much as architecture. Separating reusable form data from template-specific export rules made the interface manageable while still respecting more than 90 different document layouts and their exact cell requirements.