Low Confidence in 3D Analyst "minus" tool results

[ErinWelch]

I am expecting to see some differences between these two DEMs.  I am using the 3D analyst tool "minus".  Both input DEMs are floating point.  Each time I run this tool, the resulting DEM_minus gives me a DEM that has a high: 0 and a low: 0, which is not what I was expecting.  I am expecting some difference.  Any suggestions to get this tool to give actual difference between DEMs?

[TimBarnes]

I am expecting to see some differences between these two DEMs.  I am using the 3D analyst tool "minus".  Both input DEMs are floating point.  Each time I run this tool, the resulting DEM_minus gives me a DEM that has a high: 0 and a low: 0, which is not what I was expecting.  I am expecting some difference.  Any suggestions to get this tool to give actual difference between DEMs?

What is the output DEM number format in? If, for some reason (i.e. environmental settings) it has been set to int, then this could explain the apparent lack of difference?

[DanPatterson_Retired]

as suggested, float them both and ensure that they have the same coordinate system and cell size