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How can I get Mathcad to recongnize transconductance?

DarrellH
1-Newbie

How can I get Mathcad to recongnize transconductance?

I'm new to Mathcad and can't fingure this out. If anyone can give a quick answer I'd really appreciate it.

I defined Gblk1:=8mhos using the "mho" symbol from the insert unit pull down menu. But on the next line, when I type in Iblk1=Vinput*Gblk1, it states that this is an undefined value. Any clues why it doesn't recongnize Gblk1?

Other questions:

1. Is there a quick keystroke to get common symbols like the Ohm symbol, etc without having to go thru the pull down menu each time?

2. When I take a defined value and move it to another part of the sheet, if it is lower vertically the equations on the top side don't work. Is there a way to get Mathcad to use defined values regardless of where they are on the sheet?

Thanks for your help.

Darrell

4 REPLIES 4
LucMeekes
23-Emerald III
(To:DarrellH)

It helps to attach a worksheet, to see where problems lie.

To answer your other questions:

1. To get an omega symbol, type a "W" followed by [CTRL-G] (for "greek")

2. You can have global definitions, instead of typing ":" which normally results in the ":=" symbol, type "~", which results in a "triple equals" (three, instead of two dashes on top of each other), constituting a global definition.

Success!

Luc

Darrell Hambley wrote:

I'm new to Mathcad and can't fingure this out. If anyone can give a quick answer I'd really appreciate it.

I defined Gblk1:=8mhos using the "mho" symbol from the insert unit pull down menu. But on the next line, when I type in Iblk1=Vinput*Gblk1, it states that this is an undefined value. Any clues why it doesn't recongnize Gblk1?

Other questions:

1. Is there a quick keystroke to get common symbols like the Ohm symbol, etc without having to go thru the pull down menu each time?

2. When I take a defined value and move it to another part of the sheet, if it is lower vertically the equations on the top side don't work. Is there a way to get Mathcad to use defined values regardless of where they are on the sheet?

Thanks for your help.

Darrell

It works for me!

Open this sheet. If it works in your version, then you typed something wrong!

StuartBruff
23-Emerald II
(To:DarrellH)

Darrell Hambley wrote:

I'm new to Mathcad and can't fingure this out. If anyone can give a quick answer I'd really appreciate it.

I defined Gblk1:=8mhos using the "mho" symbol from the insert unit pull down menu. But on the next line, when I type in Iblk1=Vinput*Gblk1, it states that this is an undefined value. Any clues why it doesn't recongnize Gblk1?

Hi Darrell,

Part of the problem with answering questions from people new to Mathcad is that we don't actually know what you've done unless we have the worksheet to look at. There are several ways in which a user could make an error that isn't apparent from just looking at it (using a literal subscript instead of an indicial subscript is a common one).

In your case, for example, 'mhos' is not the correct unit, it's just 'mho'. Without knowing that you had used the menu, this would be an obvious source of the problem to an experienced user. If you could post the worksheet (preferably in M11 format as well as whatever version you use (assuming it's at least M11)), that would help people find the problem.

I've typed in what I think you meant to enter:

Gblk1 := 8 mho

Vinput := 5 V

lblk1 := Vinput*Gblk1

and it seems to work, giving

lblk1 = 40 A

Other questions:

1. Is there a quick keystroke to get common symbols like the Ohm symbol, etc without having to go thru the pull down menu each time?

Depends on the unit. You can normally just type in the unit name or symbol. If it's Greek, then you can type in the Roman letter equivalent then type ctl-G, which turn into Greek; for example, to get ohm type capital W then ctl-G. See attached worksheet.

2. When I take a defined value and move it to another part of the sheet, if it is lower vertically the equations on the top side don't work. Is there a way to get Mathcad to use defined values regardless of where they are on the sheet?

Not in general. Mathcad works left to right, top to bottom. However, Mathcad evaluates a worksheet in two passess. In the first pass, you can use what is called a 'Global Define' (three parallel lines - either use the Evaluation toolbar or type '~'). Mathcad evaluates these in the same order as normal definitions, but they are available to use in normal definitions (evaluated during the second pass). Again, see example in the attached worksheet.

There are also 'tricks' using components, but they're probably best left until you gain experience using Mathcad.

Stuart

Thanks for the help guys. I had mistakenly typed ; instead of :

dumb newbie!

Darrell

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