The SF light is glowing continuously and Diagnostic buffer shows Sense voltage is minimum.

Dear experts,

The MLFB no of the Siwarex U module is 7MH4 950-2AA01

The problem we are facing that when the Load cell cable is not connected the Exc. Voltage is 11.7 volt. Moment we connect the load cell cable the Sense and Exc both drop to 6.7 Volt. Even we tried with a shorting of sense and Exc. in panel without field connection and same result was happening.

The SF light is glowing continuously and Diagnostic buffer shows Sense voltage is minimum.

With warm regards

ddg

Even we tried with a shorting of sense and Exc. in panel without field connection and same result was happening.

The SF light is glowing continuously and Diagnostic buffer shows Sense voltage is minimum.

Thank you for your reply. First of all we found that the module is a new one from Siemens (from 2007), which have an excitation voltage of 6 volt in state of 10 volt. Due to the lack of information we faced the problem. Now the issue is the existing Load cell specification shows allowable supply voltage is 10 to 30 Volts. My quarries are

1. If the supply voltage is less than specified voltage is there any problem?
2. What will be the resolution of analog to digital convention of the module?

With Warm regards

Thanks both of you for your prompt reply.

First of all the SF light is now off.
I am getting 6.04 volt across sense and excitation both(when Load cell is connected) and 11.67 Volt across the excitation (when Load cell is disconnected).

Now the issue is,
The specification of the load cell as below

Can we use this module for this particular load cell?

With warm regards

ddg

Thanks a lot

With Warm regards

ddg

Hi Siwarexi / SonicRanger,

We are commissioning the batch house with Schenk RTN load cell(s) withthe Siwarex U module. Thanks for your contribution.

Now I am having with some queries

1. In one of our Weigh hopper the load cell capacity is 22ton and the weight of the hopper + max material weight will be 10 tons. Now for 10 ton the load cell will give about (6*2.85*10)/22 mV = 7.77 mV. The calibration test weight for the Weigh hopper is 7 ton (7+1.5 ton for hopper).

As the proposed max mV will be within 8 mV can we configure the channel as 2mV/V.?

I think in this case the accuracy will be in a higher side.

1. The internal resolution of the channel is 65535 that mean the internal scale is 2427 to 65535 (to ensure the load cell nor loaded). As S7 considering the sign bit we wrote a small program to view the raw count

L PIW 698 // Raw count from Siwarex U

T DB1.DBW 12

//..

L DB1.DBD10 // RAW count in S7

Now in a weigh hopper when we select 4mV/V it is showing near13000 counts and for 2mV/V it’s near 23000.

As per our thinking the count equation for 2mV/V is 2427 + (X*Y)

For 4mV/V is 2427 + (Z*Y)

Where Y= mV from load cell

X=2Z

Please ensure our view

With best regards

ddg