This script can be used a synthetic read-only transaction against an Excel workbook in a document library.

Test-ExcelServices.ps1

function Test-ExcelServices
{
    [cmdletbinding()]
    param
    (
        [parameter(Mandatory=$true)][System.Uri]$Uri,
        [parameter(Mandatory=$false)][System.Management.Automation.PSCredential]$Credential, # if you don't want to connect as the current user
        [parameter(Mandatory=$false)][int]$CacheThreshold = 5 # minutes
    )

    begin
    {
        $correlationId = $null
    }
    process
    {
        $responseText = $null

        try
        {
            $reqeust = [System.Net.HttpWebRequest][System.Net.HttpWebRequest]::Create( $url )

            if( -not $Credential )
            {
                $reqeust.Credentials = [System.Net.CredentialCache]::DefaultCredentials
            }
            else
            {
                $reqeust.Credentials = $Credential
            }

            $response = $reqeust.GetResponse()

            try
            {
                $correlationId = $response.Headers.GetValues( "SPRequestGuid" )
                $stream        = $response.GetResponseStream()
                $reader        = New-Object System.IO.StreamReader( $stream )
                $responseText  = $reader.ReadToEnd()
            
                Write-Verbose -Message "CorrelationId:               $correlationId"
            }
            finally
            {
                if( $stream )   { $stream.Dispose()   }
                if( $reader )   { $reader.Dispose()   }
                if( $response ) { $response.Dispose() }
            }
        }
        catch
        {
            Write-Error "Error making request to $Uri. Exception: $($_.Exception)"
            return $false
        }

        if( $responseText -match "Correlation ID" )
        {
            Write-Error "SharePoint returned an exception. Correlation ID: $correlationId"
            return $false
        }

        if( $responseText )
        {
            $parsedResponseDate = Get-Date

            try
            {
                $xml = [xml]$responseText
                $namespaceManager = New-Object System.Xml.XmlNamespaceManager( $xml.NameTable )
                $namespaceManager.AddNamespace("x", "http://schemas.microsoft.com/office/2008/07/excelservices/rest" )
                
                $node = $xml.SelectSingleNode( "//x:range/x:row[1]/x:c/x:fv", $namespaceManager )
                $workbookResponseDate = $node.'#text'

                Write-Verbose -Message "Service Response Date Value: $workbookResponseDate"

            
                if( $workbookResponseDate -and [DateTime]::TryParse( $workbookResponseDate, [ref] $parsedResponseDate ) )
                {
                    $dateDifference = (Get-Date) - $parsedResponseDate
                    Write-Verbose -Message "Parsed Date Value:           $($parsedResponseDate.ToString('MM/dd/yyyy hh:mm'))"
                    Write-Verbose -Message "Current Date Time:           $(Get-Date -Format 'MM/dd/yyyy hh:mm')"
                    
                    if( $dateDifference.TotalMinutes -lt $CacheThreshold )
                    {
                        Write-Verbose -Message "Difference:                  $([Math]::Round( $dateDifference.TotalMinutes, 2 )) minutes"
                        return $true
                    }
                }
            }
            catch
            {
                Write-Error "Error parsing Excel Services Response. Exception: $($_.Exception)"
            }
        }
        else
        {
            Write-Error "No response text was returned from Excel Services."
        }

        return $false
    }
    end
    {
    }
}

# sample format to let SharePoint decide if it should use WOPI or Excel Services to fetch the data from the workbook
$url = "https://sharepoint.contoso.com/sites/teamsite/_vti_bin/ExcelRest.aspx/Shared Documents/HealthCheck.xlsx/Model/Ranges('HealthCheck')?`$format=atom"

# sample format to use WOPI to fetch the data from the workbook
$url = "https://sharepoint.contoso.com/sites/teamsite/_layouts/15/WopiFrame.aspx?sourcedoc=https://sharepoint.contoso.com/sites/teamsite/Shared Documents/HealthCheck.xlsx&action=rest&framemode=proxy&wdRestPart=Model/Ranges('HealthCheck')&wdRestQuery=`$format=atom"

# sample format to always use Excel Services to fetch the data from the workbook
$url = "https://sharepoint.contoso.com/sites/teamsite/_layouts/15/XlRestInternal.aspx?id=https://sharepoint.contoso.com/sites/teamsite/Shared%20Documents/HealthCheck.xlsx&action=rest&framemode=proxy&wdRestPart=Model/Ranges('HealthCheck')&wdRestQuery=`$format=atom"


Test-ExcelServices -Uri $url -Verbose