Solver (17BII, 27S, etc) equation with multiple outputs

[Dave Britten]

Generally speaking, I've seen two approaches to creating multi-output equations. It should be noted that this is multi-output - I haven't seen a good way to select from multiple possible sets of inputs in a single equation.

1. Use the L() function to set the value of an auxiliary variable which you can RCL after solving. Your initial formula is a good example:

DBGAIN=20xLOG(L(VGAIN:VOUT/VIN))+0xVGAIN

You can solve for DBGAIN, VOUT, or VIN, and after solving, you can press RCL VGAIN to see the voltage gain. Solving for VGAIN directly will not work, and VGAIN also can't be used as an input here.

2. Use the S() function to check which variable is being solved for and react accordingly. For instance, this equation lets you solve for either DBGAIN or VGAIN:

IF(S(DBGAIN):DBGAIN=20*LOG(VOUT/VIN):VGAIN=VOUT/VIN)

You can also solve for VOUT or VIN, but only by using VGAIN as one of the inputs.

The third alternative, which isn't really a multi-output equation at all, is to simply store multiple equations.

VGAIN=VOUT/VIN
DBGAIN=20*LOG(VOUT/VIN)

Variables will be shared between equations as long as the names are consistent, so this is often a good solution. It's like the HP 48 multiple-equation solver, but you have to figure out which equations need to be solved to get all the variables you need.