Appendix A - Signal Range Tables | LabJack

# Appendix A - Signal Range Tables

The following tables cover most common situations with the LJTIA, but for other cases there is an online tool available at analog.com:

"+Vs" = VS (typically 5.0 volts), "-Vs" = 0, "Vref" = Voffset (0.4 or 1.25 volts), “Vcm” = Vcm, and “Vdiff” = Vin.  Our definitions of Vin, Vcm, and Voffset, can be found on the main page of the LJTIA datasheet.

The output amplifiers on the LJTIA have a range of about 0.01 volts to 4.5 volts (VS-0.5 actually).

The "Low" column on the left in the tables below is the minimum Vin.  Usually this is the Vin that results in the minimum Vout of 0.01 volts, but sometimes there are other limiting factors, so the "Low" column on the right shows the Vout corresponding to each Vin.

The "High 2.5V" and "High 4.5V" columns on the left are listing the upper limit of Vin that results in a Vout of 2.5 or 4.5 volts, although sometimes there other limiting factors and those Vout values cannot be achieved.  The columns on the right list the actual Vout that results from the Vin values on the left.

Example:  Assume Voffset of the LJTIA is set to 0.4V and gain of the LJTIA is set to x11.  Assume the Vin signals come from a bridge with 5 volt excitation, so Vcm is 2.5 volts.  According to the latest tool from analog.com, the signal voltage can go from about -0.018V to +0.309V.  Beyond those limits generates an error.  Note that the table below shows similar values of -0.035 to +0.327, which are not exactly the same likely because they come from an older version of the calculator.

Table A1.1. Voffset = 0.4V

 Vcm Vin (Differential) (Volts) Vout (Single Ended) (Volts) Gain Low High 2.5 V High 4.5V Low High 2.5V High 4.5V 0V 1 -0.3 0.3 N/A 0.01 0.7 N/A 11 -0.0354 0.116 N/A 0.0106 1.58 N/A 51 -0.00764 0.0231 N/A 0.0104 1.58 N/A 201 -0.00194 0.00587 N/A 0.0101 1.58 N/A 1.25V 1 -0.39 2.1 3.68 0.01 2.5 4.08 11 -0.0354 0.191 0.334 0.0106 2.5 4.07 51 -0.00764 0.0412 0.0712 0.0104 2.5 4.08 201 -0.00194 0.0104 0.0183 0.0101 2.5 4.07 2.5V 1 -0.39 2.1 3.6 0.01 2.5 4 11 -0.0354 0.191 0.327 0.0106 2.5 4 51 -0.00764 0.0412 0.0803 0.0104 2.5 4.5 201 -0.00194 0.0104 0.0179 0.0101 2.5 4 Vin/2 1 -0.15 2.05 4.1 0.25 2.5 4.5 11 -0.0354 0.118 N/A 0.0106 1.7 N/A 51 -0.00764 0.024 N/A 0.0104 1.59 N/A 201 -0.00194 0.0059 N/A 0.0101 1.59 N/A

Table A1.2. Voffset = 1.25V

 Vcm Vin (Differential) (Volts) Vout (Single Ended) (Volts) Gain Low High 2.5 V High 4.5V Low High 2.5V High 4.5V 0V 1 -0.3 0.3 N/A 0.95 1.55 N/A 11 -0.107 0.107 N/A 0.073 2.43 N/A 51 -0.0231 0.0231 N/A 0.0719 2.43 N/A 201 -0.005879 0.00587 N/A 0.0701 2.43 N/A 1.25V 1 -1.24 1.25 3.25 0.01 2.5 4.5 11 -0.112 0.114 0.295 0.018 2.5 4.5 51 -0.0243 0.0245 0.0637 0.0107 2.5 4.5 201 -0.00616 0.00622 0.0162 0.0114 2.5 4.5 2.5V 1 -1.24 2.1 3.25 0.01 2.5 4.5 11 -0.112 0.191 0.295 0.018 2.5 4.5 51 -0.0243 0.0412 0.0637 0.0105 2.5 4.5 201 -0.00616 0.00622 0.0161 0.0114 2.5 4.5 Vin/2 1 -0.15 1.25 4.1 1.1 2.5 4.5 11 -0.0983 0.113 0.118 0.169 2.5 2.55 51 -0.0226 0.0236 N/A 0.0974 2.45 N/A 201 -0.00584 0.0059 N/A 0.0762 2.44 N/A