Measurement Computing 6224 - Manual (Page 18)

3-4 Pinouts and Connections 6224 Users Manual
The power consumed by a single bridge is V
ex
2
/R
Where V
ex
is the excitation voltage and R is the total resistance of the bridge.
For a full bridge, R is equal to the resistance of each element. For a half or quarter bridge, R is equal to two times
the resistance of each element.
For each of the three voltage sources, the 150 mW limit allows you to power full and half bridges as follows:
Four 350 Ω half bridges at 5.0 V, or
Four 350 Ω full bridges at 3.3 V, or
Four 120 Ω half bridges at 2.5 V
If you need an excitation voltage greater than 150 mW, use the four-position external excitation voltage connectors
(see following section). Each of the three external connectors can be used to provide external excitation to four
channels of the 6224; thus all twelve channels can receive external excitation.
External Excitation Voltage Sources
The 6224 front panel includes three 4-pin connectors which provide a means of connecting external excitation
voltage sources.
Each external voltage source serves 4 channels, as follows; the first source applies excitation voltage to CH1
through CH4, the second to CH5 through CH8, and the third to CH9 through CH12. Since channels are associated
by groups of four, what you set for one channel (in a group) will also be applied to other channels of that group.
Example: if you set channel 1 for 10V external excitation, channels, 2, 3, and 4 will also have 10V external
excitation.
The sensor industry does not recognize a single standard excitation voltage level. However, excitation voltage levels
residing in the range of 2.5V to 10 V are common.
Unless you supply external excitation voltage, we recommend that you set the excitation voltage
to a value that keeps the total power below 150 mW.
The pinout and manufacturing information for the external excitation voltage source connector follows.
Contact Measurement Computing for more information.
Manufacturer Information
Molex Mating Connector
4-position housing (43025-0400)
Crimp terminal (43030-0007)
Also see the preceding section, Internal Excitation Voltage Sources.
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Silkscreen polarity orientation
markers visible on 6224 chassis
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