How can I measure the actual injected current on Bioimpedance Spectrocopy?

Hi, I want to build a Bioimpedance Spectroscopy (BIS) or Electrical Impedance Spectroscopy (EIS) using an Improved Howland Current Source for the V to I converter, and I want to measure the actual current that injected to an object (such as tissues). The fact is, injected current on an object is measured with a mathematic formula (I=V/Rx, which Rx is the load to change the voltage to current), but the voltage is using the input voltage from the source, not the voltage after the amplifying procces on OP-AMP (with assuming that OP-AMP in an ideal condition). In fact, there's no OP-AMP with ideal condition. Example, the input voltage is 1 Volt, with Rx 1 Kohm, the result of injected current is 10 mA (remember this assuming the OP-AMP in the ideal condition). So, I wanna measure the actual injected current, but how?

The current is determined by  the forcing resistor R5 (Rx?), so Iout=Vin/R5, since the buffer can be near perfect, ie, the input current could be pico amps or less. It works very well at DC with well matched resistors (try changing a  resistor and you will soon see how critical this is)  as a quick analysis in spice will show. However, the whole thing falls over at high frequencies for a number of reasons, and spice will not show this unless you take into account common mode performance, and gain band width in particular, you need to have very good models for the op amps you will be using. What frequency do you wish to go up to. The other issue would be compliance, the amplifiers saturate at some point, depending on R5 and the load resistance, and the output current will then no longer track the drive voltage. An additional circuit to monitor the voltage across R5 would pick this up. There is a good analysis here. There has been a lot of work done on this issue, if you do a search for bioimpedance and current source you will see that many papers have been written on the subject, you need to have a look at them. It is clear that this circuit  can generate the theoretical current Vin/R5 to well over 10Mhz with appropriate op amps, resistor matching, and careful design.Cheers,
Richard

The sensing subsystem makes a measurement of the voltage generated by the circulation of the current prepaidgiftbalance.

The sensing subsystem makes a measurement of the voltage generated by the circulation of the current prepaidgiftbalance.