diff --git a/src/app/app-routing.module.ts b/src/app/app-routing.module.ts
index e17a583..e4fffe7 100644
--- a/src/app/app-routing.module.ts
+++ b/src/app/app-routing.module.ts
@@ -8,6 +8,7 @@ import {DocumentationComponent} from './documentation/documentation.component';
 import {TemplatesComponent} from './templates/templates.component';
 import {SettingsComponent} from './settings/settings.component';
 import {UsersComponent} from './users/users.component';
+import {ChangelogComponent} from './changelog/changelog.component';
 
 
 const routes: Routes = [
@@ -17,6 +18,7 @@ const routes: Routes = [
   {path: 'samples/new', component: SampleComponent, canActivate: [LoginService]},
   {path: 'samples/edit/:id', component: SampleComponent, canActivate: [LoginService]},
   {path: 'templates', component: TemplatesComponent, canActivate: [LoginService]},
+  {path: 'changelog', component: ChangelogComponent, canActivate: [LoginService]},
   {path: 'users', component: UsersComponent, canActivate: [LoginService]},
   {path: 'settings', component: SettingsComponent, canActivate: [LoginService]},
   {path: 'documentation', component: DocumentationComponent},
diff --git a/src/app/app.component.html b/src/app/app.component.html
index 43aa0c7..648446a 100644
--- a/src/app/app.component.html
+++ b/src/app/app.component.html
@@ -5,6 +5,7 @@
     <a routerLink="/templates" routerLinkActive="active" rbLoadingLink *ngIf="login.isLevel.dev">
       Templates
     </a>
+    <a routerLink="/changelog" routerLinkActive="active" rbLoadingLink *ngIf="login.isLevel.dev">Changelog</a>
     <a routerLink="/users" routerLinkActive="active" rbLoadingLink *ngIf="login.isLevel.admin">Users</a>
     <a routerLink="/documentation" routerLinkActive="active" rbLoadingLink>Documentation</a>
   </nav>
@@ -32,7 +33,7 @@
         <rb-icon-button icon="mail" mode="primary" (mouseup)="closeBugReport(close)">Send report</rb-icon-button>
       </a>
     </ng-template>
-<!--    <span class="dev-label" *ngIf="devMode">DEVELOPMENT</span>-->
+    <span class="dev-label" *ngIf="devMode">DEVELOPMENT</span>
     DeFinMa
   </div>
 </rb-full-header>
diff --git a/src/app/app.module.ts b/src/app/app.module.ts
index 18590d1..79a2602 100644
--- a/src/app/app.module.ts
+++ b/src/app/app.module.ts
@@ -25,6 +25,7 @@ import { TemplatesComponent } from './templates/templates.component';
 import { ParametersPipe } from './parameters.pipe';
 import { SettingsComponent } from './settings/settings.component';
 import { UsersComponent } from './users/users.component';
+import { ChangelogComponent } from './changelog/changelog.component';
 
 @NgModule({
   declarations: [
@@ -42,7 +43,8 @@ import { UsersComponent } from './users/users.component';
     TemplatesComponent,
     ParametersPipe,
     SettingsComponent,
-    UsersComponent
+    UsersComponent,
+    ChangelogComponent
   ],
   imports: [
     LocalStorageModule.forRoot({
diff --git a/src/app/changelog/changelog.component.html b/src/app/changelog/changelog.component.html
new file mode 100644
index 0000000..9d59d0c
--- /dev/null
+++ b/src/app/changelog/changelog.component.html
@@ -0,0 +1,35 @@
+<h2>Changelog</h2>
+
+<div class="header">
+  <rb-form-date-input name="dateInput" label="older than" [options]="{enableTime: true}"
+                      [(ngModel)]="timestamp" (ngModelChange)="loadChangelog()">
+  </rb-form-date-input>
+
+  <rb-form-select name="pageSizeSelection" label="page size" [(ngModel)]="pageSize" (ngModelChange)="loadChangelog()">
+    <option value="3">3</option>
+    <option value="10">10</option>
+    <option value="25">25</option>
+    <option value="50">50</option>
+    <option value="100">100</option>
+    <option value="250">250</option>
+    <option value="500">500</option>
+  </rb-form-select>
+
+  <button class="rb-btn rb-link" type="button" (click)="loadChangelog(1)">
+    next page
+    <span class="rb-ic  rb-ic-forward-right"></span>
+  </button>
+</div>
+
+<rb-table>
+  <tr>
+    <th>Date</th>
+    <th>Action</th>
+    <th>Data</th>
+  </tr>
+  <tr *ngFor="let entry of changelog">
+    <td>{{entry.date}}</td>
+    <td>{{entry.action}}</td>
+    <td>{{entry.data | json}}</td>
+  </tr>
+</rb-table>
diff --git a/src/app/changelog/changelog.component.scss b/src/app/changelog/changelog.component.scss
new file mode 100644
index 0000000..c36c6b1
--- /dev/null
+++ b/src/app/changelog/changelog.component.scss
@@ -0,0 +1,10 @@
+.header {
+
+  & > * {
+    float: left;
+  }
+
+  button {
+    float: right;
+  }
+}
diff --git a/src/app/changelog/changelog.component.spec.ts b/src/app/changelog/changelog.component.spec.ts
new file mode 100644
index 0000000..a9ebfb6
--- /dev/null
+++ b/src/app/changelog/changelog.component.spec.ts
@@ -0,0 +1,25 @@
+import { async, ComponentFixture, TestBed } from '@angular/core/testing';
+
+import { ChangelogComponent } from './changelog.component';
+
+describe('ChangelogComponent', () => {
+  let component: ChangelogComponent;
+  let fixture: ComponentFixture<ChangelogComponent>;
+
+  beforeEach(async(() => {
+    TestBed.configureTestingModule({
+      declarations: [ ChangelogComponent ]
+    })
+    .compileComponents();
+  }));
+
+  beforeEach(() => {
+    fixture = TestBed.createComponent(ChangelogComponent);
+    component = fixture.componentInstance;
+    fixture.detectChanges();
+  });
+
+  it('should create', () => {
+    expect(component).toBeTruthy();
+  });
+});
diff --git a/src/app/changelog/changelog.component.ts b/src/app/changelog/changelog.component.ts
new file mode 100644
index 0000000..55da828
--- /dev/null
+++ b/src/app/changelog/changelog.component.ts
@@ -0,0 +1,32 @@
+import { Component, OnInit } from '@angular/core';
+import {ChangelogModel} from '../models/changelog.model';
+import {ApiService} from '../services/api.service';
+
+@Component({
+  selector: 'app-changelog',
+  templateUrl: './changelog.component.html',
+  styleUrls: ['./changelog.component.scss']
+})
+export class ChangelogComponent implements OnInit {
+
+  timestamp = new Date();
+  pageSize = 25;
+  changelog: ChangelogModel[] = [];
+
+  constructor(
+    private api: ApiService
+  ) { }
+
+  ngOnInit(): void {
+    this.loadChangelog();
+  }
+
+  loadChangelog(page = 0) {
+    this.api.get<ChangelogModel[]>(`/changelog/${this.timestamp.toISOString()}/${page}/${this.pageSize}`, data => {
+      this.changelog = data.map(e => new ChangelogModel().deserialize(e));
+      this.timestamp = new Date(this.changelog[0].date);
+      console.log(this.changelog);
+    });
+  }
+
+}
diff --git a/src/app/models/changelog.model.spec.ts b/src/app/models/changelog.model.spec.ts
new file mode 100644
index 0000000..49eea17
--- /dev/null
+++ b/src/app/models/changelog.model.spec.ts
@@ -0,0 +1,7 @@
+import { ChangelogModel } from './changelog.model';
+
+describe('ChangelogModel', () => {
+  it('should create an instance', () => {
+    expect(new ChangelogModel()).toBeTruthy();
+  });
+});
diff --git a/src/app/models/changelog.model.ts b/src/app/models/changelog.model.ts
new file mode 100644
index 0000000..3ed5c21
--- /dev/null
+++ b/src/app/models/changelog.model.ts
@@ -0,0 +1,9 @@
+import {BaseModel} from './base.model';
+
+export class ChangelogModel extends BaseModel {
+  date: Date;
+  action: string;
+  collection: string;
+  conditions: {[key: string]: any};
+  data: {[key: string]: any};
+}
diff --git a/src/app/sample/sample.component.html b/src/app/sample/sample.component.html
index aae27cd..017fa35 100644
--- a/src/app/sample/sample.component.html
+++ b/src/app/sample/sample.component.html
@@ -19,16 +19,17 @@
     <div class="material shaded-container" *ngIf="newMaterial" [@inOut]>
       <h4>Material properties</h4>
       <rb-form-input name="supplier" label="supplier"
-                     [rbFormInputAutocomplete]="autocomplete.bind(this, d.arr.materialSupplier)"
+                     [rbFormInputAutocomplete]="autocomplete.bind(this, d.arr.materialSuppliers)"
                      [rbDebounceTime]="0" [rbInitialOpen]="true" appValidate="string" required
                      [(ngModel)]="material.supplier" #supplierInput="ngModel"
-                     (focusout)="checkTypo('materialSuppliers', 'supplier', modalWarning)">
+                     (focusout)="checkTypo($event, 'materialSuppliers', 'supplier', modalWarning)">
         <ng-template rbFormValidationMessage="failure">{{supplierInput.errors.failure}}</ng-template>
       </rb-form-input>
-      <rb-form-input name="group" label="group" [rbFormInputAutocomplete]="autocomplete.bind(this, d.arr.materialGroup)"
+      <rb-form-input name="group" label="group"
+                     [rbFormInputAutocomplete]="autocomplete.bind(this, d.arr.materialGroups)"
                      [rbDebounceTime]="0" [rbInitialOpen]="true" appValidate="string" required
                      [(ngModel)]="material.group" #groupInput="ngModel"
-                     (focusout)="checkTypo('materialGroups', 'group', modalWarning)">
+                     (focusout)="checkTypo($event, 'materialGroups', 'group', modalWarning)">
         <ng-template rbFormValidationMessage="failure">{{groupInput.errors.failure}}</ng-template>
       </rb-form-input>
       <ng-template #modalWarning>
@@ -44,7 +45,7 @@
       </rb-array-input>
       <rb-form-select name="conditionSelect" label="Type"
                       [(ngModel)]="material.properties.material_template">
-        <option *ngFor="let m of d.arr.materialTemplates" [value]="m._id">{{m.name}}</option>
+        <option *ngFor="let m of d.latest.materialTemplates" [value]="m._id">{{m.name}}</option>
       </rb-form-select>
       <rb-form-input *ngFor="let parameter of d.id.materialTemplates[material.properties.material_template].parameters;
                      index as i" [name]="'materialParameter' + i"
@@ -157,7 +158,7 @@
         <div *ngIf="gSample.condition.condition_template" [@inOut]>
           <rb-form-select name="conditionSelect" label="Condition"
                           [(ngModel)]="gSample.condition.condition_template">
-            <option *ngFor="let c of d.arr.conditionTemplates" [value]="c._id">{{c.name}}</option>
+            <option *ngFor="let c of d.latest.conditionTemplates" [value]="c._id">{{c.name}}</option>
           </rb-form-select>
 
           <ng-container *ngFor="let parameter of
@@ -186,7 +187,7 @@
           <rb-form-select [name]="'measurementTemplateSelect-' + gIndex + '-' + mIndex" label="Template"
                           [(ngModel)]="measurement.measurement_template"
                           (ngModelChange)="clearMeasurement(gIndex, mIndex)">
-            <option *ngFor="let m of d.arr.measurementTemplates" [value]="m._id">{{m.name}}</option>
+            <option *ngFor="let m of d.latest.measurementTemplates" [value]="m._id">{{m.name}}</option>
           </rb-form-select>
 
           <div *ngFor="let parameter of d.id.measurementTemplates[measurement.measurement_template].parameters;
diff --git a/src/app/sample/sample.component.ts b/src/app/sample/sample.component.ts
index fea0e0d..67c2b85 100644
--- a/src/app/sample/sample.component.ts
+++ b/src/app/sample/sample.component.ts
@@ -139,7 +139,7 @@ export class SampleComponent implements OnInit, AfterContentChecked {
     });
     this.d.load('materialTemplates', () => {
       if (!this.material.properties.material_template) {
-        this.material.properties.material_template = this.d.arr.materialTemplates.filter(e => e.name === 'plastic').reverse()[0]._id;
+        this.material.properties.material_template = this.d.latest.materialTemplates.find(e => e.name === 'plastic')._id;
       }
       this.loading--;
     });
@@ -270,6 +270,8 @@ export class SampleComponent implements OnInit, AfterContentChecked {
     }
     new Promise<void>(resolve => {
       if (this.newMaterial) {  // save material first if new one exists
+        console.log(this.material);
+        this.material.numbers = this.material.numbers.filter(e => e !== '');
         this.api.post<MaterialModel>('/material/new', this.material.sendFormat(), data => {
           this.d.arr.materials.push(data);  // add material to data
           this.material = data;
@@ -348,7 +350,7 @@ export class SampleComponent implements OnInit, AfterContentChecked {
     else {  // no matching material found
       if (this.sample.material_id !== null) {  // reset previous match
         this.material = new MaterialModel();
-        this.material.properties.material_template = this.d.arr.materialTemplates.filter(e => e.name === 'plastic').reverse()[0]._id;
+        this.material.properties.material_template = this.d.latest.materialTemplates.find(e => e.name === 'plastic')._id;
       }
       this.sample.material_id = null;
     }
@@ -376,9 +378,9 @@ export class SampleComponent implements OnInit, AfterContentChecked {
   // add a new measurement for generated sample at index
   addMeasurement(gIndex) {
     this.generatedSamples[gIndex].measurements.push(
-      new MeasurementModel(this.d.arr.measurementTemplates.filter(e => e.name === 'spectrum').reverse()[0]._id)
+      new MeasurementModel(this.d.latest.measurementTemplates.find(e => e.name === 'spectrum')._id)
     );
-    this.generatedSamples[gIndex].measurements[this.generatedSamples[gIndex].measurements.length - 1].values.device = this.defaultDevice;
+    console.log(this.d.latest.measurementTemplates.find(e => e.name === 'spectrum'));
     if (!this.charts[gIndex]) {  // add array if there are no charts yet
       this.charts[gIndex] = [];
     }
@@ -411,6 +413,8 @@ export class SampleComponent implements OnInit, AfterContentChecked {
             this.addMeasurement(gIndex);
             index = this.generatedSamples[gIndex].measurements.length - 1;
           }
+          this.generatedSamples[gIndex].measurements[index].values.device =
+            this.generatedSamples[gIndex].measurements[mIndex].values.device;
           this.generatedSamples[gIndex].measurements[index].values.filename = files[i].name;
           this.generatedSamples[gIndex].measurements[index].values[parameter] =
             fileReader.result.toString().split('\r\n').map(e => e.split(','));
@@ -430,12 +434,15 @@ export class SampleComponent implements OnInit, AfterContentChecked {
       sample.condition.condition_template = null;
     }
     else {
-      sample.condition.condition_template = this.d.arr.conditionTemplates[0]._id;
+      sample.condition.condition_template = this.d.latest.conditionTemplates[0]._id;
     }
   }
 
-  checkTypo(list, mKey, modal: TemplateRef<any>) {
-    if (this.d.arr[list].indexOf(this.material[list]) < 0) {  // entry is not in list
+  checkTypo(event, list, mKey, modal: TemplateRef<any>) {
+    // user did not click on suggestion and entry is not in list
+    if (!(event.relatedTarget && (event.relatedTarget.className.indexOf('rb-dropdown-item') >= 0 ||
+        event.relatedTarget.className.indexOf('close-btn rb-btn rb-passive-link') >= 0)) &&
+      this.d.arr[list].indexOf(this.material[mKey]) < 0) {
       this.modalText.list = mKey;
       this.modalText.suggestion = this.d.arr[list]  // find possible entry from list
         .map(e => ({v: e, s: strCompare.sorensenDice(e, this.material[mKey])}))
diff --git a/src/app/services/data.service.ts b/src/app/services/data.service.ts
index 497b643..1313baa 100644
--- a/src/app/services/data.service.ts
+++ b/src/app/services/data.service.ts
@@ -15,19 +15,20 @@ export class DataService {
   ) { }
 
   private collectionMap = {
-    materials: {path: '/materials?status=all', model: MaterialModel, array: true},
-    materialSuppliers: {path: '/material/suppliers', model: null, array: true},
-    materialGroups: {path: '/material/groups', model: null, array: true},
-    materialTemplates: {path: '/template/materials', model: TemplateModel, array: true},
-    measurementTemplates: {path: '/template/measurements', model: TemplateModel, array: true},
-    conditionTemplates: {path: '/template/conditions', model: TemplateModel, array: true},
-    sampleNotesFields: {path: '/sample/notes/fields', model: TemplateModel, array: true},
-    users: {path: '/users', model: UserModel, array: true},
-    user: {path: '/user', model: UserModel, array: false},
-    userKey: {path: '/user/key', model: BaseModel, array: false}
+    materials: {path: '/materials?status=all', model: MaterialModel, type: 'array'},
+    materialSuppliers: {path: '/material/suppliers', model: null, type: 'array'},
+    materialGroups: {path: '/material/groups', model: null, type: 'array'},
+    materialTemplates: {path: '/template/materials', model: TemplateModel, type: 'template'},
+    measurementTemplates: {path: '/template/measurements', model: TemplateModel, type: 'template'},
+    conditionTemplates: {path: '/template/conditions', model: TemplateModel, type: 'template'},
+    sampleNotesFields: {path: '/sample/notes/fields', model: TemplateModel, type: 'array'},
+    users: {path: '/users', model: UserModel, type: 'array'},
+    user: {path: '/user', model: UserModel, type: 'string'},
+    userKey: {path: '/user/key', model: BaseModel, type: 'string'}
   };
 
   arr: {[key: string]: any[]} = {};  // array of data
+  latest: {[key: string]: any[]} = {};  // array of latest template versions
   id: {[key: string]: {[id: string]: any}} = {};  // data in format _id: data
   d: {[key: string]: any} = {};      // data not in array format
 
@@ -37,10 +38,24 @@ export class DataService {
     }
     else {  // load data
       this.api.get<any>(this.collectionMap[collection].path, data => {
-        if (this.collectionMap[collection].array) {  // array data
+        if (this.collectionMap[collection].type !== 'string') {  // array data
           this.arr[collection] = data
             .map(e => this.collectionMap[collection].model ? new this.collectionMap[collection].model().deserialize(e) : e);
           this.idReload(collection);
+          if (this.collectionMap[collection].type === 'template') {
+            const tmpTemplates = {};
+            this.arr[collection].forEach(template => {
+              if (tmpTemplates[template.first_id]) {  // already found another version
+                if (template.version > tmpTemplates[template.first_id].version) {
+                  tmpTemplates[template.first_id] = template;
+                }
+              }
+              else {
+                tmpTemplates[template.first_id] = template;
+              }
+            });
+            this.latest[collection] = Object.values(tmpTemplates);
+          }
         }
         else {  // not array data
           this.d[collection] = new this.collectionMap[collection].model().deserialize(data);
diff --git a/src/app/services/login.service.ts b/src/app/services/login.service.ts
index bced041..05b14f3 100644
--- a/src/app/services/login.service.ts
+++ b/src/app/services/login.service.ts
@@ -11,6 +11,7 @@ export class LoginService implements CanActivate {
 
   private pathPermissions = [
     {path: 'templates', permission: 'dev'},
+    {path: 'changelog', permission: 'dev'},
     {path: 'users', permission: 'admin'}
   ];
   readonly levels = [
diff --git a/src/app/services/validation.service.ts b/src/app/services/validation.service.ts
index 070e3a5..47134e2 100644
--- a/src/app/services/validation.service.ts
+++ b/src/app/services/validation.service.ts
@@ -122,6 +122,7 @@ export class ValidationService {
     const {ignore, error} = Joi.string()
       .max(128)
       .invalid('condition_template', 'material_template')
+      .allow('')
       .pattern(/^[^.]+$/)
       .required()
       .messages({'string.pattern.base': 'name must not contain a dot'})
diff --git a/src/app/templates/templates.component.html b/src/app/templates/templates.component.html
index 6d71ebc..7a6b46e 100644
--- a/src/app/templates/templates.component.html
+++ b/src/app/templates/templates.component.html
@@ -55,7 +55,8 @@
             <rb-icon-button icon="edit" mode="secondary" (click)="group.edit = !group.edit">
               Edit template
             </rb-icon-button>
-            <rb-icon-button icon="save" mode="primary" (click)="saveTemplate(group.first_id)" *ngIf="group.edit">
+            <rb-icon-button icon="save" mode="primary" (click)="saveTemplate(group.first_id)" *ngIf="group.edit"
+                            [disabled]="templateForm.invalid">
               Save template
             </rb-icon-button>
           </form>
diff --git a/src/app/templates/templates.component.ts b/src/app/templates/templates.component.ts
index f858665..5782be6 100644
--- a/src/app/templates/templates.component.ts
+++ b/src/app/templates/templates.component.ts
@@ -5,6 +5,7 @@ import {animate, style, transition, trigger} from '@angular/animations';
 import {ValidationService} from '../services/validation.service';
 import cloneDeep from 'lodash/cloneDeep';
 import omit from 'lodash/omit';
+import {DataService} from '../services/data.service';
 
 @Component({
   selector: 'app-templates',
@@ -36,7 +37,8 @@ export class TemplatesComponent implements OnInit {
 
   constructor(
     private api: ApiService,
-    private validate: ValidationService
+    private validate: ValidationService,
+    public d: DataService
   ) { }
 
   ngOnInit(): void {
@@ -44,8 +46,8 @@ export class TemplatesComponent implements OnInit {
   }
 
   loadTemplates() {
-    this.api.get<TemplateModel[]>(`/template/${this.collection}s`, data => {
-      this.templates = data;
+    this.d.load(this.collection + 'Templates', () => {
+      this.templates = this.d.arr[this.collection + 'Templates'];
       this.templateFormat();
     });
   }
@@ -99,6 +101,7 @@ export class TemplatesComponent implements OnInit {
             this.templates.push(data);
           }
           this.templateFormat();
+          this.d.idReload(this.collection + 'Templates');
         });
       }
       else {
@@ -107,6 +110,7 @@ export class TemplatesComponent implements OnInit {
             this.templates.push(data);
           }
           this.templateFormat();
+          this.d.idReload(this.collection + 'Templates');
         });
       }
     }