| CPC A61M 5/3146 (2013.01) [A61M 5/20 (2013.01); A61M 5/24 (2013.01); A61M 5/31511 (2013.01); A61M 2005/2411 (2013.01); A61M 2205/215 (2013.01); A61M 2205/3368 (2013.01); A61M 2205/6018 (2013.01); A61M 2205/6054 (2013.01); A61M 2205/6063 (2013.01); A61M 2205/6072 (2013.01)] | 18 Claims |

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1. An auto injector for administering a medicament, comprising:
a housing;
a cartridge receiver configured to receive a cartridge assembly comprising a cartridge and a cartridge code feature, wherein the cartridge contains the medicament;
a code sensor configured to read the cartridge code feature;
a drive module coupled to move a plunger rod;
a resistance sensor configured to provide a resistance signal indicative of resistance against movement of the plunger rod and a processing unit coupled to the code sensor, the drive module and to the resistance sensor;
wherein the processing unit is configured to:
receive the resistance signal and determine the resistance against movement of the plunger rod based on the resistance signal;
receive from the code sensor a code signal indicative of the cartridge code feature; and
control the drive module to move the plunger rod to a first plunger rod position based on the resistance signal, wherein the first plunger rod position is based on the code signal, and wherein the first plunger rod position is selected to expel air from the cartridge.
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