I instantiate two cube objects to act as a caliper measuring device in a PI script

public void InstantiateCalipersAtDistance()
    {
        if (headCamera != null)
        {
            float heightInMeters = participantHeightCm / 100f;
            float distance = heightInMeters; // Distance in front of the participant
            Vector3 headPosition = headCamera.transform.position; // Get the head camera position
            Vector3 forward = transform.forward;

            Vector3 baseCaliperPosition = headPosition + forward * distance;
            caliperSeparationDistance = Random.Range(0.05f, 0.25f); // Random distance between 0.05 and 0.25 meters

            baseCaliper = Instantiate(baseCaliperPrefab, baseCaliperPosition, Quaternion.identity);
            movingCaliper = Instantiate(movingCaliperPrefab, baseCaliperPosition + new Vector3(0, caliperSeparationDistance, 0), Quaternion.identity);
        }
        else
        {
            Debug.LogError("Head camera is not assigned.");
        }
    }

The top caliper can be moved up and down but the base caliper stays put in a CC script

 void Update()
    {
        if (canMoveUp)
        {
            if (Input.GetKey(KeyCode.UpArrow))
            {
                transform.Translate(0, speed * Time.deltaTime, 0);

            }
        }
        if (canMoveDown)
        {
            if (Input.GetKey(KeyCode.DownArrow))
            {
                transform.Translate(0, -speed * Time.deltaTime, 0);

            }
        }
        
    void OnCollisionEnter(Collision collision)
    {
        if (collision.gameObject.name == "BaseCaliper(Clone)")
        {
            canMoveDown = false;


        }

    }
    void OnCollisionExit(Collision collision)
    {
        if (collision.gameObject.name == "BaseCaliper(Clone)")
        {
            canMoveDown = true;


        }

    }

I want to record the distance between the calipers continuously, even when the top one is moving. I tried to do this with a script I got from elsewhere, which I put on the moving (top) caliper object with the Obj field in the inspector having the bottom caliper assigned to it[enter image description here](https://i.sstatic.net/A211jBW8.png).

using UnityEngine;

public class LiveDistanceBetweenCalipers : MonoBehaviour
{
    
    [SerializeField] public GameObject obj; // Reference to the other caliper (base caliper)

    public float yDistanceBetweenObjects; // Variable to store the Y distance

    private void Update()
    {
        if (obj != null)
        {
            // Calculate the Y distance between this object (moving caliper) and the other object (base caliper)
            yDistanceBetweenObjects = Mathf.Abs(transform.position.y - obj.transform.position.y);

            // Print the Y distance to the console
            Debug.Log("Y Distance between calipers: " + yDistanceBetweenObjects);

            // Optionally, draw a line between the objects for visualization
            Debug.DrawLine(transform.position, obj.transform.position, Color.green);
        }
        else
        {
            Debug.LogWarning("Reference to the other caliper (base caliper) is missing.");
        }
    }

  
}

It seems to continually track a distance but I am pretty sure it is wrong as the line points to a different position in the scene form the top caliper, and the numbers I get don’t make sense relative to the distance.

Screenshots should hopefully make what I want to to more understandable if anyone can offer an assist.