Question about SIRIUS STGM Voltage Differential

Hi,

I am trying to connect the differential MEMS accelerometer(MEAS 4610) to SIRIUS STGM Voltage Differential.

[ Figure 01. MEAS 4610 Schematic ]

I found the wire connection for STGM Voltage Differential in SIRIUS Manual v22-3, page 185.

[ Figure 02. SIRIUS' STGM Voltage Differential ]

I also read the guide about STGM Voltage Differential as follows.

"Use only when sensor Output (+) and Output (-) are referenced to Gnd. Gnd must be connected."

As explained above, it is understood to mean connecting Output (+) and Output (-) to GND, respectively, as follows.

[ Figure 03. GND reference for Output (+) and Output (-) ]

If Output (+) and Output (-) are connected to GND respectively, it seems to mean to configure differential input with a "Floating Signal Source". 

If the "Floating Signal Source" configuration is correct, I guess there must be a resistor between Output (+) and GND and Output (-) and GND.

[ Figure 04. Differential connection for "Floating Signal Source" ]

And I wonder if the resistor between Output (+), Output (-) and GND is unnecessary or unnecessary.

[ Figure 05. Resistor between Output (+) (-) and GND ]

Does SIRIUS already have the resistors needed to configure the "Floating Signal Source" inside GND?

[ Figure 06. Inside resistor of GND ]

Based on my guesses, I drew up a block diagram connecting the MEAS 4610 to STGM Voltage Differential. 

I am wondering if this configuration is correct.

[ Figure 07. Connecting MEAS 4610 to STGM, Voltage Differential ]

Finally, I don't understand the solid line connecting the shield and the SIRIUS in STGM Volatage Differential. 

What exactly does this solid line mean?

[ Figure 08. Solid Line between Shield and SIRIUS ]

Best regards

Hey Daniel-

I am only familiar with the STGS, so maybe there is something I am not aware of with the STGM but I think this will still apply for you-

I can't say that I understand the manual's heavily used comment of "Use only when sensor Output (+) and Output (-) are referenced to Gnd. Gnd must be connected." I could be wrong here and have something to learn as well but I don't believe it is suggesting to connect the signal wires to ground, with or without resistors. DEWESoft rep's, can you confirm this?

I use differential accelerometers with our STG slices in a 4 wire configuration, two wires for excitation and two wires for signal. The diagram I reference for this is found directly on the setup page within DEWESoft X as seen in the screenshot I attached.

DEWESoft side pins-

PIN

(2) Positive signal from the transducer to the slice's input

(7) Negative signal from the transducer to the slice's input

(1) Positive excitation from the slice to power the transducer

(6) Jumpered to pin 1 as close to the sensor as you can get it. If your cable does not have enough conductors (EG- it has less than 6 conductors) then this jumper is done at the DB9 connector on the slice

(8) Negative excitation from the slice to power the transducer

(3) Jumpered to pin 8 as close to the sensor as you can get it. Our cables only have 5 conductors so these jumpers are done at the DB9 connector on the slice

(4) If your sensor has a dedicated ground wire (not all sensors have this), or you have the ability to connect the sensor's case (via the connector or otherwise), it would connect to Pin 4. I don't use pin 4.

The "Solid line" you reference is the shield in your cable, assuming your instrument cable has a shield. It is implying that you connect the shield to the ground of the Data logger's chassis. Be careful with this, if your shield is connected to the case of the transducer you might create an undesirable ground loop; which is likely why the illustration only shows the solid line/wire connecting to the slice and not the transducer.

-M

Dear Daniel,

just to be sure we have asked the HW team for some help. Below are the answers:

[ Figure 07. Connecting MEAS 4610 to STGM, Voltage Differential ]

Finally, I don't understand the solid line connecting the shield and the SIRIUS in STGM Volatage Differential. 

What exactly does this solid line mean?

The schematic is OK. We would recommend using a 100kR resistor, but there are not necessary. Maybe some noise or CMR would be better in certain conditions.

About shielding:

The shield of the cable needs to be connected to the metal part of the DSUB9 connector.

What exactly does this solid line mean?

[ Figure 08. Solid Line between Shield and SIRIUS ]

The solid line is DSUB9 metal housing or backshell.

Best Regards.