Hello all:
I have put together a circuit using INA125 and ADS1115 to measure the output of a load cell. I am using INA125 to provide a 10V excitation voltage to the load cell. I am measuring both the excitation votage and the output of the load cell using ADS1115. I have powered the circuit from a 12V 5 amp-hrs lead acid battery. I am attaching my circuit diagram. However, I am encountering some unexpected results. My excitation voltage drops as time progresses. I would expect INA125 to provide a regulated 10V reference voltage. Below are the results. Note that the digital reading is the excitation voltage measured using a trim pot whose output has been buffered using an op-amp to provide a high-impedance input to ADC:
date digital reading imputed votage ref voltage
Tue Apr 7 12:20:26 2015 9793 1.22 10.00
Tue Apr 7 12:26:33 2015 9686 1.21 9.89
Tue Apr 7 12:32:30 2015 9790 1.22 10.00
Tue Apr 7 12:38:46 2015 9784 1.22 9.99
Tue Apr 7 14:09:16 2015 9606 1.20 9.81
Tue Apr 7 14:18:13 2015 9624 1.20 9.83
Tue Apr 7 14:23:53 2015 9633 1.20 9.84
Tue Apr 7 14:29:26 2015 9629 1.20 9.83
Tue Apr 7 14:34:49 2015 9611 1.20 9.81
Tue Apr 7 14:48:32 2015 9598 1.20 9.80
Tue Apr 7 14:55:08 2015 9561 1.20 9.76
Tue Apr 7 15:13:01 2015 9563 1.20 9.77
Tue Apr 7 15:18:53 2015 9558 1.19 9.76
Tue Apr 7 15:24:34 2015 9558 1.19 9.76
Tue Apr 7 15:30:03 2015 9552 1.19 9.75
Tue Apr 7 15:39:18 2015 9543 1.19 9.74
Tue Apr 7 15:45:04 2015 9531 1.19 9.73
Tue Apr 7 15:50:43 2015 9513 1.19 9.71
Tue Apr 7 15:56:28 2015 9491 1.19 9.69
Tue Apr 7 16:15:57 2015 9479 1.18 9.68
Tue Apr 7 16:22:21 2015 9427 1.18 9.63
Tue Apr 7 16:28:27 2015 9432 1.18 9.63
Tue Apr 7 16:35:10 2015 9432 1.18 9.63
Tue Apr 7 16:41:31 2015 9411 1.18 9.61
Tue Apr 7 16:52:22 2015 9393 1.17 9.59
Tue Apr 7 17:04:10 2015 9340 1.17 9.54
Tue Apr 7 17:10:30 2015 9348 1.17 9.55
Tue Apr 7 17:21:12 2015 9326 1.17 9.52
I have put together a circuit using INA125 and ADS1115 to measure the output of a load cell. I am using INA125 to provide a 10V excitation voltage to the load cell. I am measuring both the excitation votage and the output of the load cell using ADS1115. I have powered the circuit from a 12V 5 amp-hrs lead acid battery. I am attaching my circuit diagram. However, I am encountering some unexpected results. My excitation voltage drops as time progresses. I would expect INA125 to provide a regulated 10V reference voltage. Below are the results. Note that the digital reading is the excitation voltage measured using a trim pot whose output has been buffered using an op-amp to provide a high-impedance input to ADC:
date digital reading imputed votage ref voltage
Tue Apr 7 12:20:26 2015 9793 1.22 10.00
Tue Apr 7 12:26:33 2015 9686 1.21 9.89
Tue Apr 7 12:32:30 2015 9790 1.22 10.00
Tue Apr 7 12:38:46 2015 9784 1.22 9.99
Tue Apr 7 14:09:16 2015 9606 1.20 9.81
Tue Apr 7 14:18:13 2015 9624 1.20 9.83
Tue Apr 7 14:23:53 2015 9633 1.20 9.84
Tue Apr 7 14:29:26 2015 9629 1.20 9.83
Tue Apr 7 14:34:49 2015 9611 1.20 9.81
Tue Apr 7 14:48:32 2015 9598 1.20 9.80
Tue Apr 7 14:55:08 2015 9561 1.20 9.76
Tue Apr 7 15:13:01 2015 9563 1.20 9.77
Tue Apr 7 15:18:53 2015 9558 1.19 9.76
Tue Apr 7 15:24:34 2015 9558 1.19 9.76
Tue Apr 7 15:30:03 2015 9552 1.19 9.75
Tue Apr 7 15:39:18 2015 9543 1.19 9.74
Tue Apr 7 15:45:04 2015 9531 1.19 9.73
Tue Apr 7 15:50:43 2015 9513 1.19 9.71
Tue Apr 7 15:56:28 2015 9491 1.19 9.69
Tue Apr 7 16:15:57 2015 9479 1.18 9.68
Tue Apr 7 16:22:21 2015 9427 1.18 9.63
Tue Apr 7 16:28:27 2015 9432 1.18 9.63
Tue Apr 7 16:35:10 2015 9432 1.18 9.63
Tue Apr 7 16:41:31 2015 9411 1.18 9.61
Tue Apr 7 16:52:22 2015 9393 1.17 9.59
Tue Apr 7 17:04:10 2015 9340 1.17 9.54
Tue Apr 7 17:10:30 2015 9348 1.17 9.55
Tue Apr 7 17:21:12 2015 9326 1.17 9.52
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