Jack Johnson, P.E.

IDAS Engineering Inc.

Jack Johnson is an electrohydraulic specialist, fluid power engineering consultant, and president of IDAS Engineering Inc., Milwaukee. Contact him at jack@idaseng.com, phone (414) 236-5350, or visit www.idaseng.com.

Articles by Jack Johnson, P.E.
Digital resolution with Hall-effect sensors, part 5
By Jack L. Johnson, P.E. Figure 1. The magnetic pickup can sense down to zero speed when it is equipped with a Hall-effect sensor. Editor's note: This is the fifth installment in a seven-part series on digital resolution and other ...
Digital resolution of rotational transducers, part 4
By Jack L. Johnson, P.E. Editor's note: This is the fourth installment in a seven-part series on digital resolution and other subjects. Read the rest now: Part 1, Part 2, Part 3, Part 5, Part 6, and Part 7. A variety of issues is associated with the ...
Digital resolution and related subjects — Part 2
Editor's note: This is the second installment in a seven-part series on digital resolution and other subjects. Read the rest now: Part 1, Part 3, Part 4, Part 5, Part 6, and Part 7. The number of bits needed in a transducer ...
Digital resolution and other digital subjects, part 1
By Jack L. Johnson, P.E. Table 1 — The total number of combinations in which N binary switches (bits) can exist is 2N. So four bits have 16 unique ways in which they can be turned on (1) or off (0). Editor's note: This ...
Questions and answers on electrohydraulic control
By Jack L. Johnson, P.E. Question: I put together a positioning system to help form pie crusts in a mass production operation. At times the system breaks into noisy and even violent vibration and oscillation. Why does that happen and how does one make ...
Use hydrostatic transmission models to determine steady-state performance
By Jack L. Johnson, P. E. To be practical, a hydrostatic transmission requires peripheral equipment, such as a supercharge pump to prevent cavitation, relief valves to prevent excessive pressure, plus a heat exchanger and filter, and a means to account ...
Understanding hydrostatic transmissions
A hydrostatic transmission (HST) exists any time a hydraulic pump is connected to and dedicated to one or more hydraulic motors. Versatility is achieved by making either or both the pump and motor(s) variable displacement. The ...
Q&As about servo and proportional valves
Got questions? So do we, but we also have answers. Electrohydraulic expert Jack L. Johnson, P. E., fields some of the recurring questions he encounters in his many educational sessions about closed-loop electrohydraulic control.
Manufacturing is still alive in the USA
A recent news item I heard on the radio announced that China will surpass the U. S. as the largest manufacturing nation in the world some time next year. If the general broadcast media are your primary source of news, you’re probably surprised that the ...
Case drain issues with pumps and motors
By Jack L. Johnson, P. E. Analytical schematics of pump and motor models were introduced in an earlier edition of “Motion Control.” Four different levels of models exist, arbitrarily numbered as Type 0 through Type 3, each one progressively more complex ...
Another look at pressure-reducing, pressure-compensated flow control valves
By Jack L. Johnson, P. E. Before concluding the discussion from last month, it will be helpful to review the equation for flow force because it begins to exert its effects on the valve performance any time pressure exceeds zero. Here is one of ...
Examining pressure-reducing, pressure-compensated flow control valves
By Jack L. Johnson, P. E. A pressure reducing, pressure compensated flow control valve is shown in a cartridge configuration in Figure 1. However, it is also manufactured in a conventional spool configuration. The operating principles are the same in ...
Understanding the unloading compensator, part 2
Summarizing last month’s discussion, Figure 1 serves as a starting point for explaining the test method used by manufacturers and users of unloading compensator valves and for the development of its math model. The basic test parameters are the 4-way ...
Understanding the unloading compensator
An unloading compensator is used with a fixed displacement pump to emulate a variable-displacement pump with load sensing — inefficiency notwithstanding.
Understanding unloading valves — Part 2
By Jack L. Johnson, P. E. To conclude our discussion of unloading valves, consider that Figure 5 adds a 4-way spool to the valve drawing of Figure 3 from last month. Note that the spool has two additional ports. They switch the sense line so that the ...
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