Due to the fact that the maximum firing rate of a single neuron is limited to 1,200 action potentials per second, as the strength of a stimulus increases, new neurons can be "recruited" thus representing the intensity of a stimulus (ie. the more neurons are recruited, the greater the intensity representation). 

Recruitment of Neurons

The intensity of a stimulus is determined by the firing rate of the receptor cells. A single neuron can represent the intensity of the stimulus by changing the frequency of action potentials transmitted (up to a limit of 150 times per second). 
- Recruiting

Johns Hopkins University

Coding is the means by which patterns of electrical activity in the sensory system convey information about the stimulus. Codes are differentiated by firing rate (seeing as action potentials themselves are "all-or-nothing").
- Intensity of Stimulus
- Location of Stimulus

Sensory Coding

Breedlove, S. & Watson, N. (2017). Behavioral neuroscience, eighth edition. Oxford University Press.

Behavioral Neuroscience 8th Edition

Intensity of Stimulus

The means by which the location of a stimulus are conveyed are determined by the knowledge of where the stimulated receptor is. This is most important in the somatosensory system, where it is highly important to know where certain stimuli originate from on our bodies. Each receptor activates pathways that convey unique positional information. The spatial properties of a stimulus are represented by labeled lines that uniquely convey spatial information.

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