diff --git a/Client/udpstreamer/static/calibration.js b/Client/udpstreamer/static/calibration.js
new file mode 100644
index 0000000..4776e5f
--- /dev/null
+++ b/Client/udpstreamer/static/calibration.js
@@ -0,0 +1,119 @@
+// Per-signal affine calibration: value = raw * scale + offset, with an optional
+// unit override. Pure and dependency-free so it can be unit-tested under Node;
+// in the browser it defines the global `Calib`.
+(function (root) {
+  'use strict';
+
+  var MAX_UNIT_LEN = 16;
+  var IDENTITY = Object.freeze({scale: 1, offset: 0, unit: ''});
+
+  // The table is keyed by (source label, base signal name). U+0000 cannot occur
+  // in either, so it is an unambiguous separator.
+  function calKey(source, signal) {
+    return source + '\u0000' + signal;
+  }
+
+  // 'Adc[3]' -> 'Adc'. One calibration covers every element of an array signal.
+  function baseSignalName(name) {
+    var s = String(name == null ? '' : name);
+    var open = s.lastIndexOf('[');
+    if (open > 0 && s.charAt(s.length - 1) === ']') {
+      var idx = s.slice(open + 1, s.length - 1);
+      if (idx.length > 0 && /^[0-9]+$/.test(idx)) return s.slice(0, open);
+    }
+    return s;
+  }
+
+  function isFiniteNum(v) {
+    return typeof v === 'number' && isFinite(v);
+  }
+
+  // Mirrors the hub-side validation exactly (Go: CalConfig.Normalise,
+  // C++: StreamHub::HandleSetCalibration). Returns null when the entry must be
+  // rejected, so a caller can revert an input field to its last accepted value.
+  function normaliseCal(obj) {
+    if (obj === null || typeof obj !== 'object') return null;
+    var source = String(obj.source == null ? '' : obj.source).trim();
+    var signal = baseSignalName(String(obj.signal == null ? '' : obj.signal).trim());
+    if (source === '' || signal === '') return null;
+    var scale = obj.scale === undefined ? 1 : obj.scale;
+    var offset = obj.offset === undefined ? 0 : obj.offset;
+    if (!isFiniteNum(scale) || scale === 0) return null;
+    if (!isFiniteNum(offset)) return null;
+    var unit = String(obj.unit == null ? '' : obj.unit).trim();
+    if (unit.length > MAX_UNIT_LEN) unit = unit.slice(0, MAX_UNIT_LEN);
+    return {source: source, signal: signal, scale: scale, offset: offset, unit: unit};
+  }
+
+  function isIdentity(cal) {
+    return cal.scale === 1 && cal.offset === 0 && cal.unit === '';
+  }
+
+  function applyCal(raw, cal) {
+    return raw * cal.scale + cal.offset;
+  }
+
+  function invertCal(value, cal) {
+    return (value - cal.offset) / cal.scale;
+  }
+
+  // A negative scale swaps the ends of a range, so re-order after calibrating.
+  function calRange(min, max, cal) {
+    var a = applyCal(min, cal), b = applyCal(max, cal);
+    return a <= b ? [a, b] : [b, a];
+  }
+
+  function CalTable() {
+    this._m = Object.create(null);
+  }
+
+  CalTable.prototype.get = function (source, signal) {
+    var e = this._m[calKey(source, baseSignalName(signal))];
+    return e === undefined ? IDENTITY : e;
+  };
+
+  // Returns false when the entry was rejected as invalid. An entry that reduces
+  // to the identity is deleted rather than stored, so a Reset cleans the table
+  // (and, once saved, the config file) instead of filling it with no-ops.
+  CalTable.prototype.set = function (entry) {
+    var c = normaliseCal(entry);
+    if (c === null) return false;
+    var k = calKey(c.source, c.signal);
+    if (isIdentity(c)) delete this._m[k];
+    else this._m[k] = c;
+    return true;
+  };
+
+  CalTable.prototype.replaceAll = function (list) {
+    this._m = Object.create(null);
+    if (!list) return;
+    for (var i = 0; i < list.length; i++) this.set(list[i]);
+  };
+
+  CalTable.prototype.list = function () {
+    var out = [], k;
+    for (k in this._m) out.push(this._m[k]);
+    out.sort(function (a, b) {
+      if (a.source !== b.source) return a.source < b.source ? -1 : 1;
+      if (a.signal !== b.signal) return a.signal < b.signal ? -1 : 1;
+      return 0;
+    });
+    return out;
+  };
+
+  var api = {
+    MAX_UNIT_LEN: MAX_UNIT_LEN,
+    IDENTITY: IDENTITY,
+    calKey: calKey,
+    baseSignalName: baseSignalName,
+    normaliseCal: normaliseCal,
+    isIdentity: isIdentity,
+    applyCal: applyCal,
+    invertCal: invertCal,
+    calRange: calRange,
+    CalTable: CalTable,
+  };
+
+  if (typeof module !== 'undefined' && module.exports) module.exports = api;
+  else root.Calib = api;
+})(typeof globalThis !== 'undefined' ? globalThis : this);
diff --git a/Client/udpstreamer/static/index.html b/Client/udpstreamer/static/index.html
index 439bc53..9805077 100644
--- a/Client/udpstreamer/static/index.html
+++ b/Client/udpstreamer/static/index.html
@@ -216,6 +216,7 @@
     </div>
     <!-- Follows the mouse over a plot: time + per-trace values. -->
     <div id="hover-readout" style="display:none"></div>
+    <script src="/calibration.js"></script>
     <script src="/app.js"></script>
   </body>
 </html>
\ No newline at end of file
diff --git a/Client/udpstreamer/test/calibration.test.js b/Client/udpstreamer/test/calibration.test.js
new file mode 100644
index 0000000..0b8e973
--- /dev/null
+++ b/Client/udpstreamer/test/calibration.test.js
@@ -0,0 +1,111 @@
+const test = require('node:test');
+const assert = require('node:assert');
+const C = require('../static/calibration.js');
+
+test('baseSignalName strips an element suffix', () => {
+  assert.strictEqual(C.baseSignalName('Adc'), 'Adc');
+  assert.strictEqual(C.baseSignalName('Adc[3]'), 'Adc');
+  assert.strictEqual(C.baseSignalName('Adc[12]'), 'Adc');
+  assert.strictEqual(C.baseSignalName('A[1]B'), 'A[1]B');
+  assert.strictEqual(C.baseSignalName(''), '');
+});
+
+test('calKey is stable and separates the two fields', () => {
+  assert.strictEqual(C.calKey('a', 'b'), C.calKey('a', 'b'));
+  assert.notStrictEqual(C.calKey('ab', 'c'), C.calKey('a', 'bc'));
+});
+
+test('normaliseCal accepts a valid entry and fills defaults', () => {
+  assert.deepStrictEqual(
+    C.normaliseCal({source: ' wave ', signal: ' Adc ', scale: 2, offset: -1, unit: ' V '}),
+    {source: 'wave', signal: 'Adc', scale: 2, offset: -1, unit: 'V'});
+  assert.deepStrictEqual(
+    C.normaliseCal({source: 'wave', signal: 'Adc'}),
+    {source: 'wave', signal: 'Adc', scale: 1, offset: 0, unit: ''});
+});
+
+test('normaliseCal strips an element suffix from the signal name', () => {
+  assert.strictEqual(C.normaliseCal({source: 'w', signal: 'Adc[3]'}).signal, 'Adc');
+});
+
+test('normaliseCal truncates an over-long unit', () => {
+  const long = 'abcdefghijklmnopqrstuvwxyz';
+  assert.strictEqual(C.normaliseCal({source: 'w', signal: 's', unit: long}).unit,
+                     long.slice(0, C.MAX_UNIT_LEN));
+});
+
+test('normaliseCal rejects invalid entries', () => {
+  assert.strictEqual(C.normaliseCal(null), null);
+  assert.strictEqual(C.normaliseCal({signal: 's'}), null);
+  assert.strictEqual(C.normaliseCal({source: 'w'}), null);
+  assert.strictEqual(C.normaliseCal({source: '  ', signal: 's'}), null);
+  assert.strictEqual(C.normaliseCal({source: 'w', signal: 's', scale: 0}), null);
+  assert.strictEqual(C.normaliseCal({source: 'w', signal: 's', scale: NaN}), null);
+  assert.strictEqual(C.normaliseCal({source: 'w', signal: 's', scale: Infinity}), null);
+  assert.strictEqual(C.normaliseCal({source: 'w', signal: 's', offset: NaN}), null);
+  assert.strictEqual(C.normaliseCal({source: 'w', signal: 's', scale: '2'}), null);
+});
+
+test('applyCal and invertCal round-trip', () => {
+  const cal = {scale: 0.5, offset: -1.25, unit: 'V'};
+  assert.strictEqual(C.applyCal(10, cal), 3.75);
+  assert.strictEqual(C.invertCal(3.75, cal), 10);
+  assert.strictEqual(C.applyCal(7, C.IDENTITY), 7);
+  assert.strictEqual(C.invertCal(7, C.IDENTITY), 7);
+});
+
+test('applyCal passes non-finite samples through untouched', () => {
+  assert.ok(Number.isNaN(C.applyCal(NaN, {scale: 2, offset: 1, unit: ''})));
+});
+
+test('calRange re-orders when the scale is negative', () => {
+  assert.deepStrictEqual(C.calRange(0, 10, {scale: 2, offset: 1, unit: ''}), [1, 21]);
+  assert.deepStrictEqual(C.calRange(0, 10, {scale: -2, offset: 1, unit: ''}), [-19, 1]);
+});
+
+test('CalTable.get returns IDENTITY for an unknown signal', () => {
+  const t = new C.CalTable();
+  assert.deepStrictEqual(t.get('w', 'Adc'), C.IDENTITY);
+});
+
+test('CalTable.get resolves an element name to its base signal', () => {
+  const t = new C.CalTable();
+  t.set({source: 'w', signal: 'Adc', scale: 3, offset: 0, unit: ''});
+  assert.strictEqual(t.get('w', 'Adc[7]').scale, 3);
+});
+
+test('CalTable.set stores, overwrites, and deletes identity entries', () => {
+  const t = new C.CalTable();
+  assert.strictEqual(t.set({source: 'w', signal: 'Adc', scale: 2}), true);
+  assert.strictEqual(t.get('w', 'Adc').scale, 2);
+  t.set({source: 'w', signal: 'Adc', scale: 5});
+  assert.strictEqual(t.get('w', 'Adc').scale, 5);
+  assert.strictEqual(t.list().length, 1);
+  // Resetting to identity removes the entry entirely.
+  assert.strictEqual(t.set({source: 'w', signal: 'Adc', scale: 1, offset: 0, unit: ''}), true);
+  assert.strictEqual(t.list().length, 0);
+  // An invalid entry is refused and changes nothing.
+  assert.strictEqual(t.set({source: 'w', signal: 'Adc', scale: 0}), false);
+  assert.strictEqual(t.list().length, 0);
+});
+
+test('CalTable.replaceAll drops the previous contents', () => {
+  const t = new C.CalTable();
+  t.set({source: 'w', signal: 'Old', scale: 2});
+  t.replaceAll([
+    {source: 'w', signal: 'B', scale: 2},
+    {source: 'w', signal: 'A', scale: 3},
+    {source: 'w', signal: 'Bad', scale: 0},
+    {source: 'w', signal: 'Ident', scale: 1, offset: 0, unit: ''},
+  ]);
+  assert.deepStrictEqual(t.list().map(e => e.signal), ['A', 'B']);
+});
+
+test('CalTable.list is sorted by source then signal', () => {
+  const t = new C.CalTable();
+  t.set({source: 'z', signal: 'a', scale: 2});
+  t.set({source: 'a', signal: 'z', scale: 2});
+  t.set({source: 'a', signal: 'b', scale: 2});
+  assert.deepStrictEqual(t.list().map(e => e.source + '/' + e.signal),
+                         ['a/b', 'a/z', 'z/a']);
+});