diff --git a/js/CCKCUtils.ts b/js/CCKCUtils.ts
index 3bfd728f..188e28ea 100644
--- a/js/CCKCUtils.ts
+++ b/js/CCKCUtils.ts
@@ -41,7 +41,7 @@ const CCKCUtils = {
    * @returns {string}
    * @public
    */
-  createCurrentReadout: function( current: number, blackBoxStudy: boolean ): string {
+  createCurrentReadout: function( current: number | null, blackBoxStudy: boolean ): string {
     if ( CCKCQueryParameters.fullPrecisionAmmeter ) {
       return current + '';
     }
diff --git a/js/view/AmmeterNode.ts b/js/view/AmmeterNode.ts
index 24bc1bbd..8e7abbd3 100644
--- a/js/view/AmmeterNode.ts
+++ b/js/view/AmmeterNode.ts
@@ -93,7 +93,7 @@ class AmmeterNode extends Node {
     );
 
     const currentReadoutProperty = new DerivedProperty( [ ammeter.currentProperty, ammeterReadoutTypeProperty ],
-      ( ( current: number, ammeterReadoutType: AmmeterReadoutType ) => {
+      ( ( current: number | null, ammeterReadoutType: AmmeterReadoutType ) => {
         return CCKCUtils.createCurrentReadout( current, options.blackBoxStudy );
       } ) );
 
diff --git a/js/view/CCKCChartNode.ts b/js/view/CCKCChartNode.ts
index 7c44f668..227120fa 100644
--- a/js/view/CCKCChartNode.ts
+++ b/js/view/CCKCChartNode.ts
@@ -38,6 +38,7 @@ import CircuitLayerNode from './CircuitLayerNode.js';
 import Property from '../../../axon/js/Property.js';
 import Bounds2 from '../../../dot/js/Bounds2.js';
 import CCKCScreenView from './CCKCScreenView.js';
+import IReadOnlyProperty from '../../../axon/js/IReadOnlyProperty.js';
 
 const oneSecondString = circuitConstructionKitCommonStrings.oneSecond;
 const timeString = circuitConstructionKitCommonStrings.time;
@@ -66,8 +67,8 @@ class CCKCChartNode extends Node {
   private backgroundDragListener: DragListener | null;
   private readonly alignProbesEmitter: Emitter<[]>;
   private readonly droppedEmitter: Emitter<[]>;
-  protected readonly aboveBottomLeft1: DerivedProperty<Vector2>;
-  protected readonly aboveBottomLeft2: DerivedProperty<Vector2>;
+  protected readonly aboveBottomLeft1: IReadOnlyProperty<Vector2>;
+  protected readonly aboveBottomLeft2: IReadOnlyProperty<Vector2>;
   private readonly zoomLevelProperty: Property<number>;
   protected readonly updatePen: () => void;
 
@@ -374,7 +375,7 @@ class CCKCChartNode extends Node {
    * @returns {CCKCProbeNode}
    * @protected
    */
-  addProbeNode( color: string, wireColor: string, dx: number, dy: number, connectionProperty: Property<Vector2>, tandem: Tandem ) {
+  addProbeNode( color: string, wireColor: string, dx: number, dy: number, connectionProperty: IReadOnlyProperty<Vector2>, tandem: Tandem ) {
     const probeNode = new CCKCProbeNode( this, this.visibleBoundsProperty, { color: color, tandem: tandem } );
 
     // Add the wire behind the probe.
diff --git a/js/view/FixedCircuitElementNode.ts b/js/view/FixedCircuitElementNode.ts
index d83355e2..feb4391d 100644
--- a/js/view/FixedCircuitElementNode.ts
+++ b/js/view/FixedCircuitElementNode.ts
@@ -65,7 +65,7 @@ class FixedCircuitElementNode extends CircuitElementNode {
   private readonly dragListener: CircuitLayerNodeDragListener | null;
   static webglSpriteNodes: Node[];
   private readonly updateHighlightVisibility: ( ( circuitElement: CircuitElement | null ) => void ) | null;
-  private readonly updateFireMultilink: Multilink | null;
+  private readonly updateFireMultilink: Multilink<[ number, number, boolean ]> | null;
 
   /**
    * @param {CCKCScreenView|null} screenView - the main screen view, null for isIcon
@@ -214,7 +214,7 @@ class FixedCircuitElementNode extends CircuitElementNode {
         if ( screenView ) {
 
           // @private {Multilink} - Show fire in batteries and resistors with resistance > 0
-          this.updateFireMultilink = Property.multilink( [
+          this.updateFireMultilink = Property.multilink<[ number, number, boolean ]>( [
             circuitElement.currentProperty,
             ( circuitElement instanceof Resistor ) ? circuitElement.resistanceProperty : ONE_AMP_PROPERTY,
             screenView.model.isValueDepictionEnabledProperty
diff --git a/js/view/VoltmeterNode.ts b/js/view/VoltmeterNode.ts
index 3e43c3c5..2574e506 100644
--- a/js/view/VoltmeterNode.ts
+++ b/js/view/VoltmeterNode.ts
@@ -111,7 +111,7 @@ class VoltmeterNode extends Node {
     } );
 
     // Displays the voltage reading
-    const voltageReadoutProperty = new DerivedProperty( [ voltmeter.voltageProperty ], ( voltage: number ) =>
+    const voltageReadoutProperty = new DerivedProperty( [ voltmeter.voltageProperty ], ( voltage: number | null ) =>
       voltage === null ? MathSymbols.NO_VALUE : CCKCUtils.createVoltageReadout( voltage )
     );