Recommendations for Field Engineer

[John Keith]

Of the models you have listed I would recommend the DM42 for its speed, precision (34 digits!) and support for solve, integrate, complex numbers and matrices. There are a seemingly endless number of modules available for the DM41X but utilizing them can be difficult for those who are not familiar with the HP-41. Also accuracy is limited to 10 digits.

If you use unit conversion in your work, the HP48/HP50 are unbeatable. They also handle complex numbers and matrices in a more intuitive way. However it is hard to find an HP48 or HP50 at a reasonable price.